Signaling of Quantization Parameters in Video Coding

ABSTRACT

A method of video processing includes determining, for a current video block of a video coded using an adaptive color transform mode, whether a joint coding of chroma residuals (JCCR) coding tool is enabled for the current video block, and performing, based on the determining, a conversion between the video and a bitstream of the video, wherein the bitstream conforms to a rule, and wherein the rule specifies that one or more quantization parameter (QP) offsets used for coding the current video block are signaled when the JCCR coding tool is enabled.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Patent ApplicationNo. PCT/CN2021/071659, filed on Jan. 14, 2021 which claims the priorityto and benefits of International Patent Application No.PCT/CN2020/072105 filed on Jan. 14, 2020. All the aforementioned patentapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

This patent document relates to image and video coding and decoding.

BACKGROUND

Digital video accounts for the largest bandwidth use on the internet andother digital communication networks. As the number of connected userdevices capable of receiving and displaying video increases, it isexpected that the bandwidth demand for digital video usage will continueto grow.

SUMMARY

The present document discloses system, methods and devices for videoencoding and decoding that include the signaling and overwriting ofquantization parameters.

In one example aspect, a method of video processing is disclosed. Themethod includes determining, for a current video block of a video codedusing an adaptive color transform (ACT) mode, whether a joint coding ofchroma residuals (JCCR) coding tool is enabled for the current videoblock, and performing, based on the determining, a conversion betweenthe video and a bitstream of the video, wherein the bitstream conformsto a rule, and wherein the rule specifies that one or more quantizationparameter (QP) offsets used for coding the current video block aresignaled when the JCCR coding tool is enabled.

In another example aspect, a method of video processing is disclosed.The method includes performing a conversion between a current videoblock of a video and a bitstream of the video, wherein the bitstreamconforms to a format rule, and wherein the format rule specifies that amanner by which a delta quantization parameter (QP) is derived orsignaled based on a coding information of the current video block.

In yet another example aspect, a method of video processing isdisclosed. The method includes performing a conversion between a currentvideo block of a video and a bitstream of the video, wherein thebitstream conforms to a format rule, and wherein the format rulespecifies that that one or more quantization parameter (QP) offsets usedfor coding the current video block are signaled in a picture parameterset (PPS) associated with the current video block independently ofinformation signaled in a sequence parameter set (SPS) associated withthe current video block.

In yet another example aspect, a method of video processing isdisclosed. The method includes performing a conversion between a currentvideo block of a video and a bitstream of the video, wherein thebitstream conforms to a format rule, and wherein the format rulespecifies a video level at which to signal one or more quantizationparameter (QP) offsets used for coding the current video block, whereinthe video level is a first level or a second level that is lower thanthe first level.

In yet another example aspect, a method of video processing isdisclosed. The method includes performing a conversion between a currentvideo block of a video and a bitstream of the video, wherein thebitstream conforms to a format rule, and wherein the format rulespecifies whether or how an overwriting mechanism is used for signalinga quantization parameter (QP) offset used for coding the current videoblock.

In yet another example aspect, a video encoder apparatus is disclosed.The video encoder comprises a processor configured to implement theabove-described methods.

In yet another example aspect, a video decoder apparatus is disclosed.The video decoder comprises a processor configured to implement theabove-described methods.

In yet another example aspect, a non-transitory computer readable mediumhaving code stored thereon is disclose. The code embodies one of themethods described herein in the form of processor-executable code.

These, and other, features are described throughout the presentdocument.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a screen content coding (SCC) decoder flow of in-loopadaptive color transform (ACT).

FIG. 2 illustrates a decoding process with the ACT.

FIG. 3 shows an example of a block coded in palette mode.

FIG. 4 shows an example of using of palette predictor to signal paletteentries.

FIG. 5 shows an example of horizontal and vertical traverse scans.

FIG. 6 shows an example of coding of palette indices.

FIG. 7 is a block diagram showing an example video processing systemaccording to various embodiments of the disclosure.

FIG. 8 is a block diagram of an example hardware platform used for videoprocessing.

FIG. 9 is a block diagram that illustrates a video coding systemaccording to various embodiments of the disclosure.

FIG. 10 is a block diagram that illustrates an encoder according tovarious embodiments of the disclosure.

FIG. 11 is a block diagram that illustrates a decoder according tovarious embodiments of the disclosure.

FIGS. 12-16 show flowcharts for example methods of video processing.

DETAILED DESCRIPTION

Section headings are used in the present document for ease ofunderstanding and do not limit the applicability of techniques andembodiments disclosed in each section only to that section. Furthermore,H.266 terminology is used in some description only for ease ofunderstanding and not for limiting scope of the disclosed techniques. Assuch, the techniques described herein are applicable to other videocodec protocols and designs also.

1. Initial Discussion

This patent document is related to image/video coding technologies.Specifically, it is related to adaptive color transform in image/videocoding. It may be applied to the standard under development, e.g.Versatile Video Coding (VVC). It may be also applicable to future videocoding standards or video codec.

2. Video Coding Introduction

Video coding standards have evolved primarily through the development ofthe well-known International Telecommunication Union (ITU)Telecommunication Standardization Sector (ITU-T) and InternationalOrganization for Standardization (ISO)/International ElectrotechnicalCommission (IEC) standards. The ITU-T produced H.261 and H.263, ISO/IECproduced MPEG-1 and MPEG-4 Visual, and the two organizations jointlyproduced the H.262/MPEG-2 Video and H.264/MPEG-4 Advanced Video Coding(AVC) and H.265/HEVC standards. Since H.262, the video coding standardsare based on the hybrid video coding structure wherein temporalprediction plus transform coding are utilized. To explore the futurevideo coding technologies beyond HEVC, Joint Video Exploration Team(JVET) was founded by video coding experts group (VCEG) and movingpictures experts group (MPEG) jointly in 2015. Since then, many newmethods have been adopted by JVET and put into the reference softwarenamed Joint Exploration Model (JEM). In April 2018, the Joint VideoExpert Team (JVET) between VCEG (Q6/16) and ISO/IEC JTC1 SC29/WG11(MPEG) was created to work on the VVC standard targeting at 50% bitratereduction compared to HEVC.

The latest version of VVC draft, i.e., Versatile Video Coding (Draft 7)could be found at:http://phenix.it-sudparis.eu/jvet/doc_end_user/documents/16_Geneva/wg11/JVET-P2001-v14.zip

The latest reference software of VVC, named VVC Test Model (VTM), couldbe found at:https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/tags/VTM-7.0

2.1. Adaptive Colour Transform (ACT) in HEVC-SCC

The Adaptive Colour Transform (ACT) was adopted into the HEVC ScreenContent Coding (SCC) test model 2 at the 18^(th) JCT-VC meeting (June30^(th) to July 9^(th), 2014, Sapporo, Japan). ACT performs in-loopcolour space conversion in the prediction residual domain using colourtransform matrices based on the YCoCg and YCoCg-R colour spaces. ACT isturned on or off adaptively at the CU level using the flagcu_residual_act_flag. ACT can be combined with Cross ComponentPrediction (CCP), which is another inter component de-correlation methodalready supported in HEVC. When both are enabled, ACT is performed afterCCP at the decoder, as shown in FIG. 1 .

2.1.1. Color Space Conversion in ACT

The colour space conversion in ACT is based on the YCoCg-R transform.Both lossy coding and lossless coding (cu_transquant_bypass_flag=0 or 1)use the same inverse transform, but an additional 1-bit left shift isapplied to the Co and Cg components in the case of lossy coding.Specifically, the following colour space transforms are used for forwardand backward conversion for lossy and lossless coding:

Forward transform for lossy coding (non-normative):

$\begin{bmatrix}Y \\{Co} \\{Cg}\end{bmatrix} = {{\begin{bmatrix}1 & 2 & 1 \\2 & 0 & {- 2} \\{- 1} & 2 & {- 1}\end{bmatrix}\begin{bmatrix}R \\G \\B\end{bmatrix}}/4}$

Forward transform for lossless coding (non-normative):

Co=R−B

t=B+(Co>>1)

Cg=(G−t)

Y=t+(Cg>>1)

Backward transform (normative):

  if(lossy){  Co = Co << 1  Cg = Cg << 1 } t     = Y − (Cg >> 1)G  =  Cg + t B =   t − (Co >> 1) R =  Co + b

The forward colour transform is not normalized, with its norm beingroughly equal to √{square root over (6)}/4 for Y and Cg and equal to√{square root over (2)}/2 for Co. In order to compensate for thenon-normalized nature of the forward transform, delta QPs of (−5, −3,−5) are applied to (Y, Co, Cg), respectively. In other words, for agiven “normal” QP for the CU, if ACT is turned on, then the quantizationparameter is set equal to (QP−5, QP−3, QP−5) for (Y, Co, Cg),respectively. The adjusted quantization parameter only affects thequantization and inverse quantization of the residuals in the CU. Fordeblocking, the “normal” QP value is still used. Clipping to 0 isapplied to the adjusted QP values to ensure that they will not becomenegative. Note that this QP adjustment is only applicable to lossycoding, as quantization is not performed in lossless coding(cu_transquant_bypass_flag=1). In SCM 4, PPS/slice-level signaling ofadditional QP offset values is introduced. These QP offset values may beused instead of (−5, −3, −5) for CUs when adaptive colour transform isapplied.

When the input bit-depths of the colour components are different,appropriate left shifts are applied to align the sample bit-depths tothe maximal bit-depth during ACT, and appropriate right shifts areapplied to restore the original sample bit-depths after ACT.

2.2. ACT in VVC

FIG. 2 illustrates the decoding flowchart of VVC with the ACT beapplied. As illustrated in FIG. 2 , the colour space conversion iscarried out in residual domain. Specifically, one additional decodingmodule, namely inverse ACT, is introduced after inverse transform toconvert the residuals from YCgCo domain back to the original domain.

In the VVC, unless the maximum transform size is smaller than the widthor height of one coding unit (CU), one CU leaf node is also used as theunit of transform processing. Therefore, in the proposed implementation,the ACT flag is signaled for one CU to select the colour space forcoding its residuals. Additionally, following the HEVC ACT design, forinter and IBC CUs, the ACT is only enabled when there is at least onenon-zero coefficient in the CU. For intra CUs, the ACT is only enabledwhen chroma components select the same intra prediction mode of lumacomponent, i.e., derived mode (DM).

The core transforms used for the colour space conversions are kept thesame as that used for the HEVC. Additionally, same with the ACT designin HEVC, to compensate the dynamic range change of residuals signalsbefore and after colour transform, the QP adjustments of (−5, −5, −3)are applied to the transform residuals.

On the other hand, the forward and inverse colour transforms may accessthe residuals of all three components. Correspondingly, in the proposedimplementation, the ACT may be disabled in the following two scenarioswhere not all residuals of three components are available.

-   -   1. Separate-tree partition: when separate-tree is applied, luma        and chroma samples inside one CTU are partitioned by different        structures. This results in that the CUs in the luma-tree only        contains luma component and the CUs in the chroma-tree only        contains two chroma components.    -   2. Intra sub-partition prediction (ISP): the ISP sub-partition        is only applied to luma while chroma signals are coded without        splitting. In the current ISP design, except the last ISP        sub-partitions, the other sub-partitions only contain luma        component.

The texts of a coding unit in the VVC draft are shown as below.

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, cqtDepth, treeType,modeType ) {  chType = treeType = = DUAL_TREE_CHROMA ? 1 : 0  if(slice_type != | | sps_ibc_enabled_flag ) {   if( treeType !=DUAL_TREE_CHROMA &&     ( ( !( cbWidth = = 4 && cbHeight == 4 ) &&modeType != MODE_TYPE_INTRA )        | | ( sps_ibc_enabled_flag &&cbWidth <= 64 && cbHeight <= 64 ) ) )     cu_skip_flag[ x0 ][ y0 ] ae(v)  if( cu_skip_flag[ x0 ][ y0 ] == 0 && slice_type != I    && !( cbWidth== 4 && cbHeight == 4 ) && modeType = = MODE_TYPE_ALL )    pred_mode_flag ae(v)   if( ( ( slice_type == I && cu_skip_flag[ x0][ y0 ] = =0 ) | |        ( slice_type != I && ( CuPredMode[ chType ][x0 ][ y0 ] != MODE_INTRA | |         ( ( ( cbWidth = = 4 && cbHeight = =4 ) | | modeType = = MODE_TYPE_INTRA )           && cu_skip_flag[ x0 ][y0 ] == 0 ) ) ) ) &&       cbWidth <= 64 && cbHeight <= 64 && modeType!= MODE_TYPE_INTER &&      sps_ibc_enabled_flag && treeType !=DUAL_TREE_CHROMA )     pred_mode_ibc_flag ae(v)  }  if( CuPredMode[chType ][ x0 ][ y0 ] == MODE_INTRA && sps_palette_enabled_flag &&  cbWidth <= 64 && cbHeight <= 64 && cu_skip_flag[ x0 ][ y0 ] = = 0 &&  modeType != MODE_TYPE_INTER )     pred_mode_plt_flag ae(v)  }  if(CuPredMode[ chType ][ x0 ][ y0 ] = = MODE_INTRA && sps_act_enabled_flag&&   treeType == SINGLE_TREE )   cu_act_enabled_flag  if( CuPredMode[chType ][ x0 ][ y0 ] = = MODE_INTRA | |   CuPredMode[ chType ][ x0 ][ y0] = = MODE_PLT ) {   if( treeType = = SINGLE_TREE | | treeType = =DUAL_TREE_LUMA ) {     if( pred_mode_plt_flag ) {        palette_coding(x0, y0, cbWidth, cbHeight, treeType )     } else {        if(sps_bdpcm_enabled_flag &&           cbWidth <= MaxTsSize && cbHeight <=MaxTsSize )          intra_bdpcm_luma_flag ae(v)        if(intra_bdpcm_luma_flag )          intra_bdpcm_luma_dir_flag ae(v)       else {          if( sps_mip_enabled_flag )          intra_mip_flag[ x0 ][ y0 ] ae(v)          if( intra_mip_flag[x0 ][ y0 ] ) {           intra_mip_transposed[ x0 ][ y0 ] ae(v)          intra_mip_mode[ x0 ][ y0 ] ae(v)          } else {          if( sps_mrl_enabled_flag && ( ( y0 % CtbSizeY ) > 0 ) )           intra_luma_ref_idx[ x0 ][ y0 ] ae(v)           if(sps_isp_enabled_flag && intra_luma_ref_idx[ x0 ][ y0 ] == 0 &&           (cbWidth <= MaxTbSizeY && cbHeight <= MaxTbSizeY )           &&            ( cbWidth * cbHeight > MinTbSizeY * MinTbSizeY) && !cu_act_enabled_flag )            intra_subpartitions_mode_flag[ x0][ y0 ] ae(v)           if( intra_subpartitions_mode_flag[ x0 ][ y0 ] == 1 )            intra_subpartitions_split_flag[ x0 ][ y0 ] ae(v)          if( intra_luma_ref_idx[ x0 ][ y0 ] = = 0 )           intra_luma_mpm_flag[ x0 ][ y0 ] ae(v)           if(intra_luma_mpm_flag[ x0 ][ y0 ] ) {            if( intra_luma_ref_idx[x0 ][ y0 ] = = 0 )             intra_luma_not_planar_flag[ x0 ][ y0 ]ae(v)            if( intra_luma_not_planar_flag[ x0 ][ y0 ] )            intra_luma_mpm_idx[ x0 ][ y0 ] ae(v)           } else           intra_luma_mpm_remainder[ x0 ][ y0 ] ae(v)          }       }     }   }   if( ( treeType == SINGLE_TREE | | treeType ==DUAL_TREE_CHROMA ) &&        ChromaArrayType != 0 ) {     if(pred_mode_plt_flag && treeType = = DUAL_TREE_CHROMA )       palette_coding( x0, y0, cbWidth / SubWidthC, cbHeight /SubHeightC, treeType )     else {        if( !cu_act_enabled_flag ) {         if( cbWidth <= MaxTsSize && cbHeight <= MaxTsSize &&          sps_bdpcm_chroma_enabled_flag ) {          intra_bdpcm_chroma_flag ae(v)           if(intra_bdpcm_chroma_flag )            intra_bdpcm_chroma_dir_flag ae(v)         } else {           if( CclmEnabled )            cclm_mode_flagae(v)           if( cclm_mode_flag )            cclm_mode_idx ae(v)          else            intra_chroma_pred_mode ae(v)          }       }     }   }  } else if( treeType != DUAL_TREE_CHROMA ) { /*MODE_INTER or MODE_IBC */   if( cu_skip_flag[ x0 ][ y0 ] = = 0 )    general_merge_flag[ x0 ][ y0 ] ae(v)   if( general_merge_flag[ x0 ][y0 ] )     merge_data( x0, y0, cbWidth, cbHeight, chType )   else if(CuPredMode[ chType ][ x0 ][ y0 ] = = MODE_IBC ) {     mvd_coding( x0,y0, 0, 0 )     if( MaxNumIbcMergeCand > l )        mvp_l0_flag[ x0 ][ y0] ae(v)     if( sps_amvr_enabled_flag &&          ( MvdL0[ x0 ][ y0 ][ 0] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ] != 0 ) )        amvr_precision_idx[ x0][ y0 ] ae(v)   } else {     if( slice_type = = B )       inter_pred_idc[ x0 ][ y0 ] ae(v)     if( sps_affine_enabled_flag&& cbWidth >= 16 && cbHeight >= 16 ) {        inter_affine_flag[ x0 ][y0 ] ae(v)        if( sps_affine_type_flag && inter_affine_flag[ x0 ][y0 ] )          cu_affine_type_flag[ x0 ][ y0 ] ae(v)     }     if(sps_smvd_enabled_flag && !mvd_l1_zero_flag &&          inter_pred_idc_[x0 ][ y0 ] = = PRED_BI &&          !inter_affine_flag[ x0 ][ y0 ] &&RefIdxSymL0 > −1 && RefIdxSymL1 > −1 )        sym_mvd_flag[ x0 ][ y0 ]ae(v)     if( inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) {        if(NumRefIdxActive[ 0 ] > 1 && !sym_mvd_flag[ x0 ][ y0 ] )         ref_idx_l0[ x0 ][ y0 ] ae(v)        mvd_coding( x0, y0, 0, 0 )       if( MotionModelIdc[ x0 ][ y0 ] > 0 )          mvd_coding( x0, y0,0, 1 )        if(MotionModelIdc[ x0 ][ y0 ] > l )          mvd_coding(x0, y0, 0, 2 )        mvp_l0_flag[ x0 ][ y0 ] ae(v)     } else {       MvdL0[ x0 ][ y0 ][ 0 ] = 0        MvdL0[ x0 ][ y0 ][ 1 ] = 0    }     if( inter_pred_idc[ x0 ][ y0 ] != PRED_L0 ) {        if(NumRefIdxActive[ 1 ] > 1 && !sym_mvd_flag[ x0 ][ y0 ] )         ref_idx_l1[ x0 ][ y0 ] ae(v)        if( mvd_l1_zero_flag &&inter_pred_idc[ x0 ][ y0 ] = = PRED_BI ) {          MvdL1[ x0 ][ y0 ][ 0] = 0          MvdL1[ x0 ][ y0 ][ 1 ] = 0          MvdCpL1[ x0 ][ y0 ][0 ][ 0 ] = 0          MvdCpL1[ x0 ][ y0 ][ 0 ][ 1 ] = 0         MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] = 0          MvdCpL1[ x0 ][ y0 ][1 ][ 1 ] = 0          MvdCpL1[ x0 ][ y0 ][ 2 ][ 0 ] = 0         MvdCpL1[ x0 ][ y0 ][ 2 ][ 1 ] = 0        } else {          if(sym_mvd_flag[ x0 ][ y0 ] ) {           MvdL1[ x0 ][ y0 ][ 0 ] = −MvdL0[x0 ][ y0 ][ 0 ]           MvdL1[ x0 ][ y0 ][ 1 ] = −MvdL0[ x0 ][ y0 ][ 1]          } else           mvd_coding( x0, y0, 1, 0 )          if(MotionModelIdc[ x0 ][ y0 ] > 0 )           mvd_coding( x0, y0, 1, 1 )         if(MotionModelIdc[ x0 ][ y0 ] > l )           mvd_coding( x0,y0, 1, 2 )        }        mvp_l1_flag[ x0 ][ y0 ] ae(v)     } else {       MvdL1[ x0 ][ y0 ][ 0 ] = 0        MvdL1[ x0 ][ y0 ][ 1 ] = 0    }     if( ( sps_amvr_enabled_flag && inter_affine_flag[ x0 ][ y0 ] == 0 &&         ( MvdL0[ x0 ][ y0 ][ 0 ] != 0 | | MvdL0[ x0 ][ y0 ][ 1 ]!= 0 | |          MvdL1[ x0 ][ y0 ][ 0 ] != 0 | | MvdL1[ x0 ][ y0 ][ 1 ]!= 0 ) ) | |        ( sps_affine_amvr_enabled_flag && inter_affine_flag[x0 ][ y0 ] = = 1 &&         ( MvdCpL0[ x0 ][ y0 ][ 0 ][ 0 ] != 0 | |MvdCpL0[ x0 ][ y0 ][ 0 ]         [ 1 ] ! = 0 | |          MvdCpL1[ x0 ][y0 ][ 0 ][ 0 ] != 0 | | MvdCpL1[ x0 ][ y0 ][ 0 ]         [ 1 ] ! = 0 | |         MvdCpL0[ x0 ][ y1 ][ 1 ][ 0 ] != 0 | | MvdCpL0[ x0 ][ y0 ][ 1 ]        [ 1 ] ! = 0 | |          MvdCpL1[ x0 ][ y0 ][ 1 ][ 0 ] != 0 | |MvdCpL1[ x0 ][ y0 ][ 1 ]         [ 1 ] ! = 0 | |          MvdCpL0[ x0 ][y0 ][ 2 ][ 0 ] != 0 | | MvdCpL0[ x0 ][ y0 ][ 2 ]         [ 1 ] ! = 0 | |         MvdCpL1[ x0 ][ y0 ][ 2 ][ 0 ] != 0 | | MvdCpL1[ x0 ][ y0 ][ 2 ]        [ 1 ] ! = 0 ) ) {        amvr_flag[ x0 ][ y0 ] ae(v)        if(amvr_flag[ x0 ][ y0 ] )          amvr_precision_idx[ x0 ][ y0 ] ae(v)    }     if( sps_bcw_enabled_flag && inter_pred_idc[ x0 ][ y0 ] = =PRED_BI &&        luma_weight_l0_flag[ ref_idx_l0 [ x0 ][ y0 ] ] = = 0&&        luma_weight_l1_flag[ ref_idx_l1 [ x0 ][ y0 ] ] == 0 &&       chroma_weight_l0_flag[ ref_idx_l0 [ x0 ][ y0 ] ] = = 0 &&       chroma_weight_l1_flag[ ref_idx_l1 [ x0 ][ y0 ] ] = = 0 &&       cbWidth * cbHeight >= 256 )        bcw_idx[ x0 ][ y0 ] ae(v)   } }  if( CuPredMode[ chType ][ x0 ][ y0 ] != MODE_INTRA &&!pred_mode_plt_flag &&   general_merge_flag[ x0 ][ y0 ] = = 0 )   cu_cbfae(v)  if( cu_cbf ) {   if( CuPredMode[ chType ][ x0 ][ y0 ] ==MODE_INTER && sps_sbt_enabled_flag      && !ciip_flag[ x0 ][ y0 ] &&!MergeTriangleFlag[ x0 ][ y0 ]      && cbWidth <= MaxTbSizeY && cbHeight<= MaxTbSizeY ) {     allowSbtVerH = cbWidth >= 8     allowSbtVerQ =cbWidth >= 16     allowSbtHorH = cbHeight >= 8     allowSbtHorQ =cbHeight >= 16     if( allowSbtVerH | | allowSbtHorH )       cu_sbt_flag ae(v)     if( cu_sbt_flag ) {        if( (allowSbtVer | | allowSbtHorH ) && ( allowSbtVerQ | | allowSbtHorQ ) )         cu_sbt_quad_flag ae(v)        if( ( cu_sbt_quad_flag &&allowSbtVerQ && allowSbtHorQ ) | |          ( !cu_sbt_quad_flag &&allowSbtVerH && allowSbtHorH ) )         cu_sbt_horizontal_flag ae(v)       cu_sbt_pos_flag ae(v)     }   }   if( sps_act_enabled_flag &&CuPredMode[ chType ][ x0 ][ y0 ] != MODE_INTRA &&     treeType ==SINGLE_TREE )     cu_act_enabled_flag ae(v)   LfnstDcOnly = 1  LfnstZeroOutSigCoeffFlag = 1   MtsZeroOutSigCoeffFlag = 1  transform_tree( x0, y0, cbWidth, cbHeight, treeType, chType )  lfnstWidth = ( treeType = = DUAL_TREE_CHROMA ) ? cbWidth / SubWidthC             : ( ( IntraSubPartitionsSplitType = = ISP_VER_SPLIT) ?cbWidth /               NumIntraSubPartitions : cbWidth )   lfnstHeight= ( treeType = = DUAL_TREE_CHROMA ) ? cbHeight / SubHeightC             : ( ( IntraSubPartitionsSplitType = = ISP_HOR_SPLIT) ?cbHeight/               NumIntraSubPartitions : cbHeight )   if( Min(lfnstWidth, lfnstHeight) >= 4 && sps_lfinst_enabled_flag = = 1 &&    CuPredMode[ chType ][ x0 ][ y0 ] == MODE_INTRA &&    transform_skip_flag[ x0 ][ y0 ][ 0 ] == 0 &&     (treeType !=DUAL_TREE_CHROMA | | !intra_mip_flag[ x0 ][ y0 ] | |        Min(lfnstWidth, lfnstHeight ) >= 16 ) &&     Max( cbWidth, cbHeight) <=MaxTbSizeY) {     if( ( IntraSubPartitionsSplitType != ISP_NO_SPLIT | |LfnstDcOnly = = 0 ) &&        LfnstZeroOutSigCoeffFlag = = 1 )       lfnst_idx ae(v)   }   if( treeType != DUAL_TREE_CHROMA && lfnstidx == 0 &&     transform_skip_flag[ x0 ][ y0 ][ 0 ] == 0 && Max(cbWidth, cbHeight ) <= 32 &&     IntraSubPartitionsSplit[ x0 ][ y0 ] ==ISP_NO_SPLIT && cu_sbt_flag = = 0 &&     MtsZeroOutSigCoeffFlag = = 1 &&tu_cbf_luma[ x0 ][ y0 ] ) {     if( ( ( CuPredMode[ chType ][ x0 ][ y0]= = MODE_INTER &&        sps_explicit_mts_inter_enabled_flag ) | |       ( CuPredMode[ chType ][ x0 ][ y0 ] == MODE_INTRA &&       sps_explicit_mts_intra_enabled_flag ) ) )        mts_idx ae(v)  }  }cu_act_enabled_flag equal to 1 specifies that the residuals of thecurrent coding unit are coded in YC_(g)C_(o) colour space.cu_act_enabled_flag equal to 0 specifies that the residuals of thecurrent coding unit are coded in original colour space. Whencu_act_enabled_flag is not present, it is inferred to be equal to 0.

2.3. Transform Skip Mode in VVC

As in HEVC, the residual of a block can be coded with transform skipmode which completely skip the transform process for a block. Inaddition, for transform skip blocks, a minimum allowed QuantizationParameter (QP) signaled in SPS is used, which is set equal to6*(internalBitDepth−inputBitDepth)+4 in VTM7.0.

2.4. Block-Based Delta Pulse Code Modulation (BDPCM)

In JVET-M0413, a block-based Delta Pulse Code Modulation (BDPCM) isproposed to code screen contents efficiently and then adopted into VVC.

The prediction directions used in BDPCM can be vertical and horizontalprediction modes. The intra prediction is done on the entire block bysample copying in prediction direction (horizontal or verticalprediction) similar to intra prediction. The residual is quantized andthe delta between the quantized residual and its predictor (horizontalor vertical) quantized value is coded. This can be described by thefollowing: For a block of size M (rows)×N (cols), let r_(i,j), 0≤i≤M−1,0≤j≤N−1 be the prediction residual after performing intra predictionhorizontally (copying left neighbor pixel value across the predictedblock line by line) or vertically (copying top neighbor line to eachline in the predicted block) using unfiltered samples from above or leftblock boundary samples. Let Q(r_(i,j)), 0≤i≤M−1, 0≤j≤N−1 denote thequantized version of the residual r_(i,j), where residual is differencebetween original block and the predicted block values. Then the blockDPCM is applied to the quantized residual samples, resulting in modifiedM×N array {tilde over (R)} with elements {tilde over (r)}_(i,j). Whenvertical BDPCM is signaled:

${\overset{\sim}{r}}_{i,j} = \left\{ {\begin{matrix}{{Q\left( r_{i,j} \right)},} & {{i = 0},{0 \leq j \leq \left( {N - 1} \right)}} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{{({i - 1})},j} \right)}},} & {{1 \leq i \leq \left( {M - 1} \right)},{0 \leq j \leq \left( {N - 1} \right)}}\end{matrix}.} \right.$

For horizontal prediction, similar rules apply, and the residualquantized samples are obtained by

${\overset{\sim}{r}}_{i,j} = \left\{ {\begin{matrix}{{Q\left( r_{i,j} \right)},} & {{0 \leq i \leq \left( {M - 1} \right)},{j = 0}} \\{{{Q\left( r_{i,j} \right)} - {Q\left( r_{i,{({j - 1})}} \right)}},} & {{0 \leq i \leq \left( {M - 1} \right)},{1 \leq j \leq \left( {N - 1} \right)}}\end{matrix}.} \right.$

The residual quantized samples {tilde over (r)}_(i,j) are sent to thedecoder.

On the decoder side, the above calculations are reversed to produceQ(r_(i,j)), 0≤i≤M−1, 0≤j≤N−1.

For vertical prediction case,

Q(r _(i,j))=Σ_(k=0) ^(i) {tilde over (r)} _(k,j), 0≤i≤(M−1), 0≤j≤(N−1).

For horizontal case,

Q(r _(i,j))=Σ_(k=0) ^(j) {tilde over (r)} _(i,k), 0≤i≤(M−1), 0≤j≤(N−1).

The inverse quantized residuals, Q⁻¹(Q(r_(i,j))), are added to the intrablock prediction values to produce the reconstructed sample values.

The main benefit of this scheme is that the inverse BDPCM can be done onthe fly during coefficient parsing simply adding the predictor as thecoefficients are parsed or it can be performed after parsing.

In VTM7.0, the BDPCM also can be applied on chroma blocks and the chromaBDPCM has a separate flag and BDPCM direction from the luma BDPCM mode.

2.5. Scaling Process for Transform Coefficients

The texts related to scaling process for transform coefficients inJVET-P2001-vE is given as follows.

Inputs to this process are:

-   -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.

Output of this process is the (nTbW)×(nTbH) array d of scaled transformcoefficients with elements d[x][y].

The quantization parameter qP is derived as follows:

-   -   If cIdx is equal to 0, the following applies:

qP=Qp′_(Y)  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:

qP=Qp′_(Cr)  (1132)

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

The variable bdOffset is derived as follows:

bdOffset=(1<<bdShift)>>1  (1139)

The list levelScale[ ][ ] is specified as levelScale[j][k]={{40, 45, 51,57, 64, 72}, {57, 64, 72, 80, 90, 102}} with j=0 . . . 1, k=0 . . . 5.

The (nTbW)×(nTbH) array dz is set equal to the (nTbW)×(nTbH) arrayTransCoeffLevel[xTbY][yTbY][cIdx].

For the derivation of the scaled transform coefficients d[x][y] with x=0. . . nTbW−1, y=0 . . . nTbH−1, the following applies:

-   -   The intermediate scaling factor m[x][y] is derived as follows:        -   If one or more of the following conditions are true, m[x][y]            is set equal to 16:            -   sps_scaling_list_enabled_flag is equal to 0.            -   pic_scaling_list_present_flag is equal to 0.            -   transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1.            -   scaling_matrix_for_lfnst_disabled_flag is equal to 1 and                lfnst_idx[xTbY][yTbY] is not equal to 0.        -   Otherwise, the following applies:            -   The variable id is derived based on predMode, cIdx,                nTbW, and nTbH as specified in Table 36 and the variable                log 2MatrixSize is derived as follows:

log 2MatrixSize=(id<2)?1:(id<8)?2:3  (1140)

-   -   -   -   The scaling factor m[x][y] is derived as follows:

m[x][y]=ScalingMatrixRec[id][i][j] with i=(x<<log 2MatrixSize)>>Log2(nTbW), j=(y<<log 2MatrixSize)>>Log 2(nTbH)  (1141)

-   -   -   -   If id is greater than 13 and both x and y are equal to                0, m[0][0] is further modified as follows:

m[0][0]=ScalingMatrixDCRec[id−14]  (1142)

-   -   NOTE—A quantization matrix element m[x][y] can be zeroed out        when any of the following conditions is true        -   x is greater than 32        -   y is greater than 32        -   The decoded tu is not coded by default transform mode (i.e.            transform type is not equal to 0) and x is greater than 16        -   The decoded tu is not coded by default transform mode (i.e.            transform type is not equal to 0) and y is greater than 16    -   The scaling factor ls[x][y] is derived as follows:        -   If pic_dep_quant_enabled_flag is equal to −1 and            transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the            following applies:

ls[x][y]=(m[x][y]*levelScale[rectNonTsFlag][(qP+1)%6])<<((qP+1)/6)  (1143)

-   -   -   Otherwise (pic_dep_quant_enabled_flag is equal to 0 or            transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1), the            following applies:

ls[x][y]=(m[x][y]*levelScale[rectNonTsFlag][qP %6])<<(qP/6)  (1144)

-   -   When BdpcmFlag[xTbY][yYbY][cIdx] is equal to 1, dz[x][y] is        modified as follows:        -   If BdpcmDir[xTbY][yYbY][cIdx] is equal to 0 and x is greater            than 0, the following applies:

dz[x][y]=Clip3(CoeffMin,CoeffMax,dz[x−1][y]+dz[x][y])  (1145)

-   -   -   Otherwise, if BdpcmDir[xTbY][yTbY][cIdx] is equal to 1 and y            is greater than 0, the following applies:

dz[x][y]=Clip3(CoeffMin,CoeffMax,dz[x][y−1]+dz[x][y])  (1146)

-   -   The value dnc[x][y] is derived as follows:

dnc[x][y]=(dz[x][y]*ls[x][y]+bdOffset)>>bdShift  (1147)

-   -   The scaled transform coefficient d[x][y] is derived as follows:

d[x][y]=Clip3(CoeffMin,CoeffMax,dnc[x][y])  (1148)

TABLE 36 Specification of the scaling matrix identifier variable idaccording to predMode, cIdx, nTbW, and nTbH max( nTbW, nTbH ) 2 4 8 1632 64 predMode = cIdx = 0 (Y) 2  8 14 20 26 MODE_INTRA cIdx = 1 (Cb) 3 9 15 21 21 cIdx = 2 (Cr) 4 10 16 22 22 predMode = cIdx = 0 (Y) 5 11 1723 27 MODE_INTER cIdx = 1 (Cb) 0 6 12 18 24 24 (INTER, IBC) cIdx = 2(Cr) 1 7 13 19 25 25

2.6. Palette Mode 2.6.1. Concept of Palette Mode

The basic idea behind a palette mode is that the pixels in the CU arerepresented by a small set of representative colour values. This set isreferred to as the palette. And it is also possible to indicate a samplethat is outside the palette by signaling an escape symbol followed by(possibly quantized) component values. This kind of pixel is calledescape pixel. The palette mode is illustrated in FIG. 3 . As depicted inFIG. 3 , for each pixel with three color components (luma, and twochroma components), an index to the palette is founded, and the blockcould be reconstructed based on the founded values in the palette.

2.6.2. Coding of the Palette Entries

For coding of the palette entries, a palette predictor is maintained.The maximum size of the palette as well as the palette predictor issignaled in the SPS. In HEVC-SCC, apalette_predictor_initializer_present_flag is introduced in the PPS.When this flag is 1, entries for initializing the palette predictor aresignaled in the bitstream. The palette predictor is initialized at thebeginning of each CTU row, each slice and each tile. Depending on thevalue of the palette_predictor_initializer_present_flag, the palettepredictor is reset to 0 or initialized using the palette predictorintializer entries signaled in the PPS. In HEVC-SCC, a palette predictorinitializer of size 0 was enabled to allow explicit disabling of thepalette predictor initialization at the PPS level.

For each entry in the palette predictor, a reuse flag is signaled toindicate whether it is part of the current palette. This is illustratedin FIG. 4 . The reuse flags are sent using run-length coding of zeros.After this, the number of new palette entries are signaled usingExponential Golomb (EG) code of order 0, i.e., EG-0. Finally, thecomponent values for the new palette entries are signaled.

2.6.3. Coding of Palette Indices

The palette indices are coded using horizontal and vertical traversescans as shown in FIG. 5 . The scan order is explicitly signaled in thebitstream using the palette_transpose_flag. For the rest of thesubsection it is assumed that the scan is horizontal.

The palette indices are coded using two palette sample modes:‘COPY_LEFT’ and ‘COPY_ABOVE’. In the ‘COPY_LEFT’ mode, the palette indexis assigned to a decoded index. In the ‘COPY_ABOVE’ mode, the paletteindex of the sample in the row above is copied. For both “COPY_LEFT’ and‘COPY_ABOVE’ modes, a run value is signaled which specifies the numberof subsequent samples that are also coded using the same mode.

In the palette mode, the value of an index for the escape symbol is thenumber of palette entries. And, when escape symbol is part of the run in‘COPY_LEFT’ or ‘COPY_ABOVE’ mode, the escape component values aresignaled for each escape symbol. The coding of palette indices isillustrated in FIG. 6 .

This syntax order is accomplished as follows. First the number of indexvalues for the CU is signaled. This is followed by signaling of theactual index values for the entire CU using truncated binary coding.Both the number of indices as well as the index values are coded inbypass mode. This groups the index-related bypass bins together. Thenthe palette sample mode (if necessary) and run are signaled in aninterleaved manner. Finally, the component escape values correspondingto the escape symbols for the entire CU are grouped together and codedin bypass mode. The binarization of escape symbols is EG coding with 3rdorder, i.e., EG-3.

An additional syntax element, last_run_type_flag, is signaled aftersignaling the index values. This syntax element, in conjunction with thenumber of indices, eliminates the need to signal the run valuecorresponding to the last run in the block.

In HEVC-SCC, the palette mode is also enabled for 4:2:2, 4:2:0, andmonochrome chroma formats. The signaling of the palette entries andpalette indices is almost identical for all the chroma formats. In caseof non-monochrome formats, each palette entry consists of 3 components.For the monochrome format, each palette entry consists of a singlecomponent. For subsampled chroma directions, the chroma samples areassociated with luma sample indices that are divisible by 2. Afterreconstructing the palette indices for the CU, if a sample has only asingle component associated with it, only the first component of thepalette entry is used. The only difference in signaling is for theescape component values. For each escape symbol, the number of escapecomponent values signaled may be different depending on the number ofcomponents associated with that symbol.

2.6.4. Palette in Dual Tree

In VVC, the dual tree coding structure is used on coding the intraslices, so the luma component and two chroma components may havedifferent palette and palette indices. In addition, the two chromacomponent shares same palette and palette indices.

2.6.5. Line Based CG Palette Mode

Line based CG palette mode was adopted to VVC. In this method, each CUof palette mode is divided into multiple segments of m samples (m=16 inthis test) based on the traverse scan mode. The encoding order forpalette run coding in each segment is as follows: For each pixel, 1context coded bin

=0 is signaled indicating if the pixel is of the same mode as theprevious pixel, i.e., if the previous scanned pixel and the currentpixel are both of run type COPY_ABOVE or if the previous scanned pixeland the current pixel are both of run type INDEX and the same indexvalue. Otherwise,

=1 is signaled. If the pixel and the previous pixel are of differentmode, one context coded bin

is signaled indicating the run type, i.e., INDEX or COPY_ABOVE, of thepixel. Same as the palette mode in VTM6.0, decoder doesn't have to parserun type if the sample is in the first row (horizontal traverse scan) orin the first column (vertical traverse scan) since the INDEX mode isused by default. Also, the decoder does not have to parse run type ifthe previously parsed run type is COPY_ABOVE. After palette run codingof pixels in one segment, the index values (for INDEX mode) andquantized escape colors are bypass coded and grouped apart fromencoding/parsing of context coded bins to improve throughput within eachline CG. Since the index value is now coded/parsed after run coding,instead of processed before palette run coding as in VTM, encoderdoesn't have to signal the number of index values

and the last run type

.

3. Technical Problems Solved by Embodiments and Solutions DescribedHerein

In some cases, the ACT and luma BDPCM modes can be enabled for oneblock. However, the chroma BDPCM mode may always be disabled on blockscoded with ACT mode. Therefore, the prediction signal may be deriveddifferently for luma and chroma blocks in the same coding unit, whichmay be less efficient.

The quantization parameter (QP) of a block may become a minus numberwhen ACT is enabled.

Some designs of ACT may not support lossless coding.

The signaling of usage of ACT may not be block size dependent.

The maximal palette size and the maximal predictor size are fixednumbers, which may limit the flexibility of palette mode.

Escape samples employs Exponential-Golomb (EG) with 3th order as thebinarization method, but the binarization for escape samples is notdependent on Quantization Parameter (QP).

4. Technical Solutions

The technical solutions described below should be considered as examplesto explain general concepts. These technical solutions should not beinterpreted in a narrow way. Furthermore, these technical solutions canbe combined in any manner.

In the following description, the term ‘block’ may represent a videoregion, such as a coding unit (CU), a prediction unit (PU), and/or atransform unit (TU), which may contain samples in three colorcomponents. The term ‘BDPCM’ is not limited to the design in VVC, but itmay present the technologies that coding residuals using differentprediction signal generation methods.

In the following description, a video block coded using a joint codingof chroma residuals (JCCR) mode includes signaling only one chromaresidual block (e.g., the Cb residual block), and the other chromaresidual block (e.g., the Cr residual block) is derived based on thesignaled chroma residual block and one or more flags (e.g., at thetransform unit level) indicating a specific JCCR mode. As described, theJCCR mode leverages the correlation between the Cb residual and the Crresidual to improve coding efficiency.

Interaction Between ACT and BDPCM (Items 1-4)

-   -   1. Whether to enable chroma BDPCM mode may depend on the usage        of ACT and/or luma BDPCM mode.        -   a. In one example, when ACT is enabled on a block, the            indication of the usage of chroma BDPCM mode (e.g.            intra_bdpcm_chroma_flag) may be inferred to be the            indication of the usage of the luma BDPCM mode (e.g.            intra_bdpcm_luma_flag).            -   i. In one example, the inferred value of chroma BDPCM                mode is defined as (ACT and luma BDPCM modes are                enabled? true: false).                -   1. In one example, the intra_bdpcm_chroma_flag may                    be set equal to false when intra_bdpcm_luma_flag is                    false.                -    a. Alternatively, the intra_bdpcm_chroma_flag may                    be set equal to true when intra_bdpcm_luma_flag is                    true.            -   ii. Alternatively, in one example, the indication of the                usage of chroma BDPCM mode may be inferred to be true if                the indication of the usage of the luma BDPCM mode and                ACT for the block are true.        -   b. Alternatively, whether to signal the usage of ACT for a            block may be conditionally checked, such as the same BDPCM            prediction direction is used for both luma and chroma            samples in the block.            -   i. Alternatively, furthermore, indication of usage of                ACT is signaled after usage of BDPCM modes.    -   2. When ACT is enabled on a block, the indication of the        prediction direction of chroma BDPCM mode (e.g.        intra_bdpcm_chroma_dir_flag) may be inferred to be the        indication of the prediction direction of the usage of the luma        BDPCM mode (e.g. intra_bdpcm_luma_dir_flag).        -   a. In one example, the inferred value of            intra_bdpcm_chroma_dir_flag is defined as (ACT is enabled?            intra_bdpcm_luma_dir_flag: 0).            -   i. In one example, the indication of the prediction                direction of chroma BDPCM mode may be inferred to                horizontal if the indication of the prediction direction                of the luma BDPCM mode is horizontal.            -   ii. Alternatively, in one example, the indication of the                prediction direction of chroma BDPCM mode may be                inferred to vertical if the indication of the prediction                direction of the luma BDPCM mode is vertical.    -   3. The ACT and BDPCM modes may be exclusively applied.        -   a. In one example, when ACT mode is enabled on a block, the            BDPCM mode may be disabled on the block.            -   i. Alternatively, furthermore, the indication of usage                of BDPCM mode may be signaled after the signaling of the                indication of usage of ACT mode.            -   ii. Alternatively, furthermore, the indication of usage                of BDPCM mode may be not signaled and inferred to false                (0).        -   b. In one example, when BDPCM mode is enabled on a block,            the ACT mode may be disabled on the block.            -   i. Alternatively, furthermore, the indication of usage                of ACT mode may be signaled after the signaling of the                indication of usage of BDPCM mode.            -   ii. Alternatively, furthermore, the indication of usage                of ACT mode may be not signaled and inferred to false                (0).        -   c. In one example, the BDPCM mode in the above examples may            denote luma BDPCM mode and/or chroma BDPCM mode.    -   4. Inverse ACT may be applied before reverse BDPCM at the        decoder.        -   a. In one example, ACT may be applied even when luma and            chroma BDPCM have a different prediction mode.        -   b. Alternatively, at the encoder, forward ACT may be applied            after BDPCM.            QP Setting when ACT is Enabled (Item 5)    -   5. It is proposed to clip the QP when ACT is enabled.        -   a. In one example, the clipping function may be defined as            (l, h, x), where l is the lowest possible value of the input            x and h is the highest possible value of the input x.            -   i. In one example, l may be set equal to 0.            -   ii. In one example, h may be set equal to 63.        -   b. In one example, the QP may be the qP given in Section            2.5.        -   c. In one example, the clipping may be performed after the            QP adjustment for ACT mode.        -   d. In one example, when transform skip is applied, l may be            set equal to the minimal allowed QP for transform skip mode.

Palette Mode Related (Item 6-7)

-   -   6. The values of maximum allowed palette size and/or maximum        allowed predictor size may depend on a coding characteristics.        Assume S₁ is the maximal palette size (or palette predictor        size) associated with a first coding characteristics; and S₂ is        the maximal palette size (or palette predictor size) associated        with a second coding characteristics.        -   a. In one example, the coding characteristics may be color            component.            -   i. In one example, the maximum allowed palette size                and/or maximum allowed predictor size for different                color components may have different values.            -   ii. In one example, the values of maximum allowed                palette size and/or maximum allowed predictor size for a                first color components (e.g., Y in YCbCr, G in RGB) may                be different from those for the other two-color                components (e.g., Cb and Cr in YCbCr, B and R in RGB)                excluding the first color component.        -   b. In one example, the coding characteristics may be the            quantization parameters (QPs).            -   i. In one example, S₁ and/or S₂ for QP₁ may be smaller                than the S₁ and/or S₂ for QP₂ if QP₁ is greater than QP₂            -   ii. In one example, the QP may be the slice level QP or                block level QP.        -   c. In one example, S₂ may be greater than or equal to S₁.        -   d. For a first coding characteristics and a second coding            characteristics, indications of maximum palette            sizes/palette predictor sizes may be signaled separately or            inferred from one to another.            -   i. In one example, S₁ may be signaled and S₂ may be                derived based on S₁.                -   1. In one example, S₂ may be inferred to S₁−n.                -   2. In one example, S₂ may be inferred to S₁>>n.                -   3. In one example, S₂ may be inferred to floor                    (S₁/n), where floor(x) denotes the maximum integer                    no larger than x.        -   e. In one example, S₁ and/or S₂ may be signaled at a high            level (e.g. SPS/PPS/PH/slice header) and adjusted at a lower            level (e.g. CU/block).            -   i. How to adjust S₁ and/or S₂ may depend on the coded                information.                -   1. How to adjust S₁ and/or S₂ may depend on the                    current QP.                -    a. In one example, the S₁ and/or S₂ may be reduced                    if the current QP is increased.                -   2. How to adjust S₁ and/or S₂ may depend on block                    dimension.                -    a. In one example, the S₁ and/or S₂ may be                    increased if the current blocks size is increased.        -   f. S₁ and/or S₂ may be dependent on whether LMCS is used.    -   7. The parameters associated with a binarization method for        escape samples/pixels may depend on coded information, e.g., the        quantization parameters (QPs).        -   a. In one example, EG binarization method may be utilized,            and the order of the EG binarization, denoted by k, may be            dependent on the coded information.            -   i. In one example, k may be reduced when the current QP                is increased.

Signaling of ACT Mode (Item 8-10)

-   -   8. Indications of the allowed maximum and/or minimum ACT size        may be signaled in        sequence/video/slice/tile/subpicture/brick/other video        processing unit level or derived based on coded information.        -   a. In one example, they may be signaled in SPS/PPS/Picture            header/slice header.        -   b. In one example, they may be conditionally signaled, such            as according to the ACT is enabled.        -   c. In one example, N-level of allowed maximum and/or minimum            ACT size may be signaled/defined, e.g., N=2.            -   i. In one example, the allowed maximum and/or minimum                ACT size may be set to either K0 or K1 (e.g., K0=64,                K1=32).            -   ii. Alternatively, furthermore, indication of the level                may be signaled, e.g., when N=2, a flag may be signaled.        -   d. In one example, indications of the differences between            the allowed maximum and/or minimum ACT size and the allowed            maximum and/or minimum transform (or transform skip) sizes            (e.g., for the luma component) may be signaled.        -   e. In one example, the allowed maximum and/or minimum ACT            size may be derived from the allowed maximum and/or minimum            (or transform skip) sizes (e.g., for the luma component).        -   f. Alternatively, furthermore, whether to and/or how to            signal indications of ACT usage and other side information            related to ACT may be dependent on the allowed maximum            and/or minimum.    -   9. When a block is greater than the allowed maximum ACT size (or        allowed maximum transform size), the block may be automatically        split to multiple sub-blocks wherein all sub-blocks share the        same prediction mode (e.g., all of them are intra coded), and        the ACT may be enabled in the sub-block level, instead of the        block level.    -   10. The indication of the usage of ACT mode may be conditionally        signaled based on the block dimensions (e.g., block width and/or        height, block width times height, ratios between block width and        height, maximum/minimum values of block width and height) and/or        maximally allowed ACT sizes.        -   a. In one example, the indication of the usage of ACT mode            may be signaled when certain conditions, e.g., according to            block dimension, are satisfied.            -   i. In one example, the conditions are if the current                block width is smaller than or equal to m and/or the                current block height is smaller than or equal to n.            -   ii. In one example, the conditions are if the current                block width times height is smaller than or no larger                than m.            -   iii. In one example, the conditions are if the current                block width times height is larger than or no smaller                than m.        -   b. Alternatively, in one example, the indication of the            usage of ACT mode may be not signaled when certain            conditions, e.g., according to block dimension, are NOT            satisfied.            -   i. In one example, the conditions are if the current                block width is larger than m and/or the current block                height is larger than n.            -   ii. In one example, the conditions are if the current                block width times height is smaller than or no larger                than m.            -   iii. In one example, the conditions are if the current                block width times height is larger than or no smaller                than m.            -   iv. Alternatively, furthermore, the indication of the                usage of ACT mode may be inferred to 0.        -   c. In above examples, the variables m, n may be pre-defined            (e.g., 4, 64, 128), or signaled, or derived on-the-fly.            -   i. In one example, m and/or n may be derived based on a                decoded message in the SPS/PPS/APS/CTU row/group of                CTUs/CU/block.                -   1. In one example, m and/or n may be set equal to                    the maximally allowed transform size (e.g.                    MaxTbSizeY).

Signaling of Constraint Flags in General Constraint Information Syntax(Item 11-16)

The constraint flags below may be signaled in a video unit other thanSPS. For example, they may be signaled in the general constraintinformation syntax specified in JVET-P2001-vE.

-   -   11. It is proposed to have a constraint flag to specify whether        the SPS ACT enabling flag (e.g., sps_act_enabled_flag) may be        equal to 0.        -   a. In one example, the flag may be denoted as            no_act_constraint_flag            -   i. When this flag is equal to 1, the SPS ACT enabling                flag (e.g., sps_act_enabled_flag) may be equal to 0.            -   ii. When this flag is equal to 0, it does not impose                such a constraint.    -   12. It is proposed to have a constraint flag to specify whether        the SPS BDPCM enabling flag (e.g., sps_bdpcm_enabled_flag) may        be equal to 0.        -   a. In one example, the flag may be denoted as            no_bdpcm_constraint_flag.            -   i. When this flag is equal to 1, the SPS BDPCM enabling                flag (e.g., sps_bdpcm_enabled_flag) may be equal to 0.            -   ii. When this flag is equal to 0, it does not impose                such a constraint.    -   13. It is proposed to have a constraint flag to specify whether        the SPS chroma BDPCM enabling flag (e.g.,        sps_bdpcm_chroma_enabled_flag) may be equal to 0.        -   a. In one example, the flag may be denoted as            no_bdpcm_chroma_constraint_flag.            -   i. When this flag is equal to 1, the SPS chroma BDPCM                enabling flag (e.g., sps_bdpcm_chroma_enabled_flag) may                be equal to 0.            -   ii. When this flag is equal to 0, it does not impose                such a constraint.    -   14. It is proposed to have a constraint flag to specify whether        the SPS palette enabling flag (e.g., sps_palette_enabled_flag)        may be equal to 0.        -   a. In one example, the flag may be denoted as            no_palette_constraint_flag.            -   i. When this flag is equal to 1, the SPS palette                enabling flag (e.g. sps_palette_enabled_flag) may be                equal to 0.            -   ii. When this flag is equal to 0, it does not impose                such a constraint.    -   15. It is proposed to have a constraint flag to specify whether        the SPS RPR enabling flag (e.g.,        ref_pic_resampling_enabled_flag) may be equal to 0.        -   a. In one example, the flag may be denoted as            no_ref_pic_resampling_constraint_flag.            -   i. When this flag is equal to 1, the SPS RPR enabling                flag (e.g. ref_pic_resampling_enabled_flag) may be equal                to 0.            -   ii. When this flag is equal to 0, it does not impose                such a constraint.    -   16. In above examples (bullet 11-15), such constraint flags may        be conditionally signaled, e.g., according to chroma format        (e.g., chroma_format_idc) and/or separate plane coding or        ChromaArrayType.

ACT QP Offset (Item 17-19)

-   -   17. It is proposed that ACT offsets may be applied after        applying other chroma offsets (e.g., those in PPS and/or picture        header (PH) and/or slice header (SH)) when ACT is applied on a        block.    -   18. It is proposed to have PPS and/or PH offsets other than −5        for JCbCr mode 2 when YCgCo color transform is applied on a        block.        -   a. In one example, the offset may be other than −5.        -   b. In one example, the offset may be indicated in PPS (e.g.,            as pps_act_cbcr_qp_offset_plus6) and the offset may be set            as pps_act_cbcr_qp_offset_plus6−6.        -   c. In one example, the offset may be indicated in PPS (e.g.,            as pps_act_cbcr_qp_offset_plus7) and the offset may be set            as pps_act_cbcr_qp_offset_plus7−7.    -   19. It is proposed to have PPS and/or PH offsets other than 1        for JCbCr mode 2 when YCgCo-R is applied on a block.        -   a. In one example, the offset may be other than −1.        -   b. In one example, the offset may be indicated in PPS (e.g.,            as pps_act_cbcr_qp_offset) and the offset may be set as            pps_act_cbcr_qp_offset.        -   c. In one example, the offset may be indicated in PPS (e.g.,            as pps_act_cbcr_qp_offset_plus1) and the offset may be set            as pps_act_cbcr_qp_offset_plus1−1.    -   20. It is proposed that when JCCR is used, the QP offset for ACT        with YCgCo transform, denoted as act_qp_offset, may depend on        JCCR mode.        -   a. In one example, when JCCR mode is 1, act_qp_offset may be            −5.            -   i. Alternatively, in one example, when JCCR mode is 1,                act_qp_offset may be −6.        -   b. In one example, when JCCR mode is 2, act_qp_offset may be            −7.            -   i. Alternatively, in one example, when JCCR mode is 2,                act_qp_offset may be                (−7−pps_joint_cbcr_qp_offset−slice_joint_cbcr_qp_offset).            -   ii. Alternatively, in one example, when JCCR mode is 2,                act_qp_offset may be                (−7+pps_joint_cbcr_qp_offset+slice_joint_cbcr_qp_offset).        -   c. In one example, when JCCR mode is 3, the ACT offset may            be −4.            -   i. Alternatively, in one example, when JCCR mode is 3,                the ACT offset may be −5.    -   21. It is proposed that when JCCR is used, the QP offset for ACT        with YCgCo-R transform, denoted as act_qp_offset, may depend on        JCCR mode.        -   a. In one example, when JCCR mode is 1, act_qp_offset may be            1.            -   i. Alternatively, in one example, when JCCR mode is 1,                act_qp_offset may be 0.        -   b. In one example, when JCCR mode is 2, act_qp_offset may be            −1.            -   i. Alternatively, in one example, when JCCR mode is 2,                act_qp_offset may be                (−1−pps_joint_cbcr_qp_offset−slice_joint_cbcr_qp_offset).            -   ii. Alternatively, in one example, when JCCR mode is 2,                act_qp_offset may be                (−1+pps_joint_cbcr_qp_offset+slice_joint_cbcr_qp_offset).        -   c. In one example, when JCCR mode is 3, the ACT offset may            be 2.            -   i. Alternatively, in one example, when JCCR mode is 3,                the ACT offset may be 1.    -   22. Whether to signal the QP offsets for ACT and JCCR coded        blocks (e.g., slice_act_cbcr_qp_offset) may depend on the        condition check of whether JCCR is enabled.        -   a. Alternatively, furthermore, the indication of whether QP            offsets for ACT and JCCR coded blocks are present (e.g.,            pps_joint_cbcr_qp_offset_present_flag/pps_slice_cbcr_qp_offset_present_flag)            may depend on the condition check of whether JCCR is            enabled.    -   23. How to derive/signal delta QPs may depend on the coded        information, such as coded mode, usage of a coding tool.        -   a. In one example, how to derive/signal delta QPs may depend            on usage of ACT for current block and/or previously coded            blocks (e.g., above and left neighboring blocks).        -   b. In one example, the derivation and/or signaling of delta            QPs may depend on whether the current block and previously            coded blocks used for QP predictor derivation share the same            coded mode or enabling/disabling status of a coding tool            (e.g., ACT).        -   c. In one example, for a current block coded with coding            tool X (e.g., ACT/Transform Skip), the QP predictor            derivation process may be different from other blocks with X            being disabled.            -   i. In one example, the QP predictor for a current block                coded with coding tool X may be derived from those                blocks with coding tool X being enabled.            -   ii. In one example, the QP predictor for a current block                coded without coding tool X may be derived from those                blocks with coding tool X being disabled.    -   24. How to signal the QP offsets in PPS may be independent from        the SPS.        -   a. Alternatively, furthermore, an indication of color format            and/or an indication of enabling of ACT may be signaled in            PPS.            -   i. Alternatively, furthermore, the QP offsets may be                signaled under the condition check of the indications.    -   25. Whether to signal the QP offsets (e.g., applied to ACT coded        blocks) in a 1st level (e.g., picture level)        -   a. It is proposed that if the QP offsets (e.g., applied to            ACT coded blocks) are present in a 2nd level (e.g., slice            level), the signaling of the QP offsets in a 1st level is            skipped.    -   26. QPs mentioned in above examples may also be present in        picture/slice/tile/subpicture level (e.g., picture        header/PPS/slice header).    -   27. Overwriting mechanism may be used for signaling QP offsets        may be utilized. That is, the QP offsets may be signaled in a        1st level (e.g., PPS), but overwritten in a 2nd level (e.g.,        Picture Header).        -   a. Alternatively, furthermore, a flag may be signaled in the            1st level or 2nd level to indicate whether overwriting is            enabled.        -   b. Alternatively, when overwriting is enabled, there may be            no need to signal the related information in the 1st level.            -   i. In one example, the QP offsets (e.g., applied to ACT                coded blocks) may not be signaled in the 1st level                (e.g., PPS) if overwritten is applied for a 2nd level                (e.g., slice).        -   c. Alternatively, furthermore, differences of QP offsets            between the 1st and 2nd level may be signaled in the 2nd            level.

General Techniques ((Items 20-21)

-   -   28. In the above examples, S₁, S₂, l, h, m, n and/or k are        integer numbers and may depend on        -   a. A message signaled in the decoding parameter set            (DPS)/SPS/video parameter set (VPS)/PPS/adaption parameter            set (APS)/picture header/slice header/tile group            header/Largest coding unit (LCU)/Coding unit (CU)/LCU            row/group of LCUs/TU/PU block/Video coding unit        -   b. Position of CU/PU/TU/block/Video coding unit        -   c. Coded modes of blocks containing the samples along the            edges        -   d. Transform matrices applied to the blocks containing the            samples along the edges        -   e. Block dimension/Block shape of current block and/or its            neighboring blocks        -   f. Indication of the colour format (such as 4:2:0, 4:4:4,            RGB or YUV)        -   g. Coding tree structure (such as dual tree or single tree)        -   h. Slice/tile group type and/or picture type        -   i. Colour component (e.g. may be only applied on Cb or Cr)        -   j. Temporal layer ID        -   k. Profiles/Levels/Tiers of a standard        -   l. Alternatively, S₁, S₂, l, h, m, n and/or k may be            signaled to the decoder.    -   29. The above proposed methods may be applied under certain        conditions.        -   a. In one example, the condition is the colour format is            4:2:0 and/or 4:2:2.        -   b. In one example, indication of usage of the above methods            may be signaled in sequence/picture/slice/tile/brick/a video            region-level, such as SPS/PPS/picture header/slice header.        -   c. In one example, the usage of above methods may depend on            -   i. Video contents (e.g. screen contents or natural                contents)            -   ii. A message signaled in the                DPS/SPS/VPS/PPS/APS/picture header/slice header/tile                group header/Largest coding unit (LCU)/Coding unit                (CU)/LCU row/group of LCUs/TU/PU block/Video coding unit            -   iii. Position of CU/PU/TU/block/Video coding unit            -   iv. Coded modes of blocks containing the samples along                the edges            -   v. Transform matrices applied to the blocks containing                the samples along the edges            -   vi. Block dimension of current block and/or its                neighboring blocks            -   vii. Block shape of current block and/or its neighboring                blocks            -   viii. Indication of the colour format (such as 4:2:0,                4:4:4, RGB or YUV)            -   ix. Coding tree structure (such as dual tree or single                tree)            -   x. Slice/tile group type and/or picture type            -   xi. Colour component (e.g. may be only applied on Cb or                Cr)            -   xii. Temporal layer ID            -   xiii. Profiles/Levels/Tiers of a standard            -   xiv. Alternatively, m and/or n may be signaled to the                decoder.

5. Embodiments

The embodiments are based on JVET-P2001-vE. The newly added texts arehighlight by

. The deleted texts are marked by italicized text.

5.1. Embodiment #1

This embodiment is related to interaction between ACT and BDPCM modes.

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, cqtDepth, treeType,modeType ) {  chType = treeType = = DUAL_TREE_CHROMA ? 1 : 0 ...  if(CuPredMode[ chType ][ x0 ][ y0 ] == MODE_INTRA &&sps_palette_enabled_flag &&    cbWidth <= 64 && cbHeight <= 64 &&cu_skip_flag[ x0 ][ y0 ] ==    0 &&    modeType != MODE_TYPE_INTER )    pred_mode_plt_flag ae(v)  }  if( CuPredMode[ chType ][ x0 ][ y0 ] ==MODE_INTRA && sps_act_enabled_flag &&   treeType == SINGLE_TREE )  cu_act_enabled_flag ae(v)  if( CuPredMode[ chType ][ x0 ][ y0 ] ==MODE_INTRA | |   CuPredMode[ chType ][ x0 ][ y0 ] = = MODE_PLT ) {   if(treeType = = SINGLE_TREE | | treeType = = DUAL_TREE_LUMA   ) {     if(pred_mode_plt_flag ) {      palette_coding( x0, y0, cbWidth, cbHeight,treeType )     } else {      if(sps_bdpcm_enabled_flag &&        cbWidth<= MaxTsSize && cbHeight <= MaxTsSize &&

      intra_bdpcm_luma_flag ae(v)      if( intra_bdpcm_luma_flag )      intra_bdpcm_luma_dir_flag ae(v)      else {        ...      }    }   } ... }

5.2. Embodiment #2

This embodiment is related to interaction between ACT and BDPCM modes.

intra_bdpcm_chroma_flag equal to 1 specifies that BDPCM is applied tothe current chroma coding blocks at the location (x0, y0), i.e. thetransform is skipped, the intra chroma prediction mode is specified byintra_bdpcm_chroma_dir_flag. intra_bdpcm_chroma_flag equal to 0specifies that BDPCM is not applied to the current chroma coding blocksat the location (x0, y0).

When intra_bdpcm_chroma_flag is not present

, it is inferred to be equal to 0.

,

.

The variable BdpcmFlag[x][y][cIdx] is set equal tointra_bdpcm_chroma_flag for x=x0 . . . x0+cbWidth−1, y=y0 . . .y0+cbHeight−1 and cIdx=1 . . . 2.

intra_bdpcm_chroma_dir_flag equal to 0 specifies that the BDPCMprediction direction is horizontal. intra_bdpcm_chroma_dir_flag equal to1 specifies that the BDPCM prediction direction is vertical.

,

.

The variable BdpcmDir[x][y][cIdx] is set equal tointra_bdpcm_chroma_dir_flag for x=x0 . . . x0+cbWidth−1, y=y0 . . .y0+cbHeight−1 and cIdx=1 . . . 2.

5.3. Embodiment #3

This embodiment is related to QP setting.

8.7.3 Scaling Process for Transform Coefficients

Inputs to this process are:

-   -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.

Output of this process is the (nTbW)×(nTbH) array d of scaled transformcoefficients with elements d[x][y].

. . . .

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

. . . .

5.4. Embodiment #4 8.7.1 Derivation Process for Quantization Parameters

. . .

-   -   The chroma quantization parameters for the Cb and Cr components,        Qp′Cb and Qp′Cr, and joint Cb-Cr coding Qp′CbCr are derived as        follows:

Qp′Cb=Clip3(−QpBdOffset,63,qPCb+pps_cb_qp_offset+slice_cb_qp_offset+CuQpOffsetCb)+QpBdOffset  (1122)

Qp′Cr=Clip3(−QpBdOffset,63,qPCr+pps_cr_qp_offset+slice_cr_qp_offset+CuQpOffsetCr)+QpBdOffset  (1123)

Qp′CbCr=Clip3(−QpBdOffset,63,qPCbCr+pps_joint_cbcr_qp_offset+slice_joint_cbcr_qp_offset+CuQpOffsetCbCr)+QpBdOffset  (1124)

5.5. Embodiment #5 7.3.9.5 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, cqtDepth, treeType,modeType ) {   chType = treeType = = DUAL_TREE_CHROMA ? 1 : 0   ...  if( CuPredMode[ chType ][ x0 ][ y0 ] == MODE_INTRA &&sps_act_enabled_flag &&     treeType = = SINGLE_TREE 

    cu_act_enabled_flag ae(v)   ...  if( cu_cbf) {     if(sps_act_enabled_flag && CuPredMode[ chType ][ x0 ][ y0 ] ! =MODE_INTRA&&      treeType = = SINGLE_TREE 

     cu_act_enabled_flag ae(v)    ...   } }

5.6. Embodiment #6 7.3.9.5 Coding Unit Syntax

Descriptor coding_unit( x0, y0, cbWidth, cbHeight, cqtDepth, treeType,modeType ) {   chType = treeType = = DUAL TREE CHROMA ? 1 : 0   ...  if( CuPredMode[ chType ][ x0 ][ y0 ] == MODE_INTRA &&sps_act_enabled_flag &&     treeType = = SINGLETREE 

      <=

    cu_act_enabled_flag ae(v)   ...  if( cu_cbf) {    if(sps_act_enabled_flag && CuPredMode[ chType ][ x0 ][ y0 ] != MODE_INTRA&&     treeType = = SINGLE TREE 

  <=

     cu_act_enabled_flag ae(v)    ...   } }

5.7. Embodiment #7 8.7.3 Scaling Process for Transform Coefficients

-   Inputs to this process are:    -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.-   Output of this process is the (nTbW)×(nTbH) array d of scaled    transform coefficients with elements d[x][y].    -   If cIdx is equal to 0, the following applies:

qP=Qp′_(Y)  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:

qP=Qp′_(Cr)  (1132)

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

The variable bdOffset is derived as follows:

bdOffset=(1<<bdShift)>>1  (1139)

The list levelScale[ ][ ] is specified as levelScale[j][k]={{40, 45, 51,57, 64, 72}, {57, 64, 72, 80, 90, 102}} with j=0 . . . 1, k=0 . . . 5.. . . .

5.8. Embodiment #8 8.7.3 Scaling Process for Transform Coefficients

-   Inputs to this process are:    -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.-   Output of this process is the (nTbW)×(nTbH) array d of scaled    transform coefficients with elements d[x][y].    -   If cIdx is equal to 0, the following applies:

qP=Qp′_(Y)  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:        -   ,

,

-   -   -   

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:        -   ,

-   -   -   

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:        -   ,

-   -   -   

qP=Qp′_(Cr)  (1132)

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

The variable bdOffset is derived as follows:

bdOffset=(1<<bdShift)>>1  (1139)

The list levelScale[ ][ ] is specified as levelScale[j][k]={{40, 45, 51,57, 64, 72}, {57, 64, 72, 80, 90, 102}} with j=0 . . . 1, k=0 . . . 5.. . . .

5.9. Embodiment #9 7.4.3.4 Picture Parameter Set RBSP Semantics

,

,

,

,

,

,

,

.

.

.

8.7.3 Scaling Process for Transform Coefficients

-   Inputs to this process are:    -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.-   Output of this process is the (nTbW)×(nTbH) array d of scaled    transform coefficients with elements d[x][y].    -   If cIdx is equal to 0, the following applies:

qP=Qp′_(Y)  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:

qP=Qp′_(Cr)  (1132)

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

,

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

,

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

The variable bdOffset is derived as follows:

bdOffset=(1<<bdShift)>>1  (1139)

The list levelScale[ ][ ] is specified as levelScale[j][k]={{40, 45, 51,57, 64, 72}, {57, 64, 72, 80, 90, 102}} with j=0 . . . 1, k=0 . . . 5.

5.10. Embodiment #10 7.4.3.4 Picture Parameter Set RBSP Semantics

,

,

,

,

,

.

,

,

.

.

.

.

.

8.7.3 Scaling Process for Transform Coefficients

-   Inputs to this process are:    -   a luma location (xTbY, yTbY) specifying the top-left sample of        the current luma transform block relative to the top-left luma        sample of the current picture,    -   a variable nTbW specifying the transform block width,    -   a variable nTbH specifying the transform block height,    -   a variable predMode specifying the prediction mode of the coding        unit,    -   a variable cIdx specifying the colour component of the current        block.-   Output of this process is the (nTbW)×(nTbH) array d of scaled    transform coefficients with elements d[x][y].    -   If cIdx is equal to 0, the following applies:

qP=Qp′Y  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:        -   

-   -   -   

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:        -   ,

,

-   -   -   

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:        -   ,

,

-   -   -   

qP=Qp′_(Cr)  (1132)

The quantization parameter qP is modified and the variablesrectNonTsFlag and bdShift are derived as follows:

-   -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=qP−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0  (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)   (1136)

rectNonTsFlag=0  (1137)

bdShift=10  (1138)

The variable bdOffset is derived as follows:

bdOffset=(1<<bdShift)>>1  (1139)

The list levelScale[ ][ ] is specified as levelScale[j][k]={{40, 45, 51,57, 64, 72}, {57, 64, 72, 80, 90, 102}} with j=0 . . . 1, k=0 . . . 5.. . . .

5.11. Embodiment #11 Syntax Change in PPS:

act enabled flag u(1) if( act_enabled_flag ) {  

u(1)  

se(v)  

se(v)  

se(v)  

u(1)   if( pps_joint_cbcr_qp_offset_present_flag && joint_cbcr_  enabled_flag)    

se(v) }

Syntax Change in Slice Header:

 if(pps_slice_act_qp_offset_present_flag && !( slicetype == I &&qtbtt_dual_tree_intra_flag) ) {   

se(v)   

se(v)   

se(v)   if( pps_joint_cbcr_qp_offset_present_flag &&sps_joint_cbcr_enabled_flag)    

se(v)  }pps_act_y_qp_offset, pps_act_cb_qp_offset, pps_act_cr_qp_offset andpps_act_cbcr_qp_offset specify the offsets to quantization parameterQp′Y, Qp′Cb, Qp′Cr and Qp′CbCr, respectively, when cu_act_enabled_flagis 1. The values of pps_act_y_qp_offset, pps_act_cb_qp_offset andpps_act_cr_qp_offset may be in the range of −12 to +12, inclusive. Whennot present, the values of pps_act_y_qp_offset, pps_act_cb_qp_offset andpps_act_cr_qp_offset are inferred to be equal to 0.pps_slice_act_qp_offsets_present_flag equal to 1 specifies thatslice_act_y_qp_offset, slice_act_cb_qp_offset, slice_act_cr_qp_offset,slice_act_cbcr_qp_offset are present in the slice header.pps_slice_act_qp_offsets_present_flag equal to 0 specifies thatslice_act_y_qp_offset, slice_act_cb_qp_offset, slice_act_cr_qp_offset,slice_act_cbcr_qp_offset are not present in the slice header. When notpresent, the value of pps_slice_act_qp_offsets_present_flag is inferredto be equal to 0.slice_act_y_qp_offset, slice_act_cb_qp_offset, slice_act_cr_qp_offsetand slice_act_cbcr_qp_offset specify the offsets when determining thevalue of the Qp′Y, Qp′Cb, Qp′Cr and Qp′CbCr quantization parameter. Thevalues of slice_act_y_qp_offset, slice_act_cb_qp_offset,slice_act_cr_qp_offset and slice_act_cbcr_qp_offset may be in the rangeof −12 to +12, inclusive. When not present, the values are inferred tobe equal to 0.

8.7.1 Derivation Process for Quantization Parameters

. . .

-   -   The variable Qp_(Y) is derived as follows:

Qp_(Y)=((qP_(Y_PRED) +CuQpDeltaVal+

+64+2*QpBdOffset)%(64+QpBdOffset))−QpBdOffset  (1116)

-   -   The luma quantization parameter Qp′_(Y) is derived as follows:

Qp′_(Y)=Qp_(Y)+QpBdOffset  (1117)

-   -   When ChromaArrayType is not equal to 0 and treeType is equal to        SINGLE_TREE or DUAL_TREE_CHROMA, the following applies:        -   When treeType is equal to DUAL_TREE_CHROMA, the variable            Qp_(Y) is set equal to the luma quantization parameter            Qp_(Y) of the luma coding unit that covers the luma location            (xCb+cbWidth/2, yCb+cbHeight/2).        -   The variables qP_(Cb), qP_(Cr) and qP_(CbCr) are derived as            follows:

qP_(Chroma)=Clip3(−QpBdOffset,63,Qp_(Y))   (1118)

qP_(Cb)=ChromaQpTable[0][qP_(Chroma)]   (1119)

qP_(Cr)=ChromaQpTable[1][qP_(Chroma)]   (1120)

qP_(CbCr)=ChromaQpTable[2][qP_(Chroma)]   (1121)

-   -   -   The chroma quantization parameters for the Cb and Cr            components, Qp′_(Cb) and Qp′_(Cr), and joint Cb-Cr coding            Qp′_(CbCr) are derived as follows:

Qp′_(Cb)=Clip3(−QpBdOffset,63,qP_(Cb)+pps_cb_qp_offset+slice_cb_qp_offset+

+QpBdOffset  (1122)

Qp′_(Cr)=Clip3(−QpBdOffset,63,qP_(Cr)+pps_cr_qp_offset+slice_cr_qp_offset+

+QpBdOffset  (1123)

Qp′_(CbCr)=Clip3(−QpBdOffset,63,qP_(CbCr)+pps_joint_cbcr_qp_offset+slice_joint_cbcr_qp_offset+

+CuQpOffset_(CbCr))+QpBdOffset   (1124)

8.7.3 Scaling Process for Transform Coefficients

. . .

.The quantization parameter qP is derived as follows:

-   -   If cIdx is equal to 0, the following applies:

qP=Qp′_(Y)  (1129)

-   -   Otherwise, if TuCResMode[xTbY][yTbY] is equal to 2, the        following applies:

qP=Qp′_(CbCr)  (1130)

-   -   Otherwise, if cIdx is equal to 1, the following applies:

qP=Qp′_(Cb)  (1131)

-   -   Otherwise (cIdx is equal to 2), the following applies:

qP=Qp′_(Cr)  (1132)

-   -   The quantization parameter qP is modified and the variables        rectNonTsFlag and bdShift are derived as follows:    -   If transform_skip_flag[xTbY][yTbY][cIdx] is equal to 0, the        following applies:

qP=

,qP−(cu_act_enabled_flag[xTbY][yTbY]?

5:0)

  (1133)

rectNonTsFlag=(((Log 2(nTbW)+Log 2(nTbH))&1)==1)?1:0   (1134)

bdShift=BitDepth+rectNonTsFlag+((Log 2(nTbW)+Log2(nTbH))/2)−5+pic_dep_quant_enabled_flag  (1135)

-   -   Otherwise (transform_skip_flag[xTbY][yTbY][cIdx] is equal to 1),        the following applies:

qP=Max(QpPrimeTs Min,qP)−(cu_act_enabled_flag[xTbY][yTbY]?5:0)  (1136)

,

FIG. 7 is a block diagram showing an example video processing system 700in which various techniques disclosed herein may be implemented. Variousimplementations may include some or all of the components of the system700. The system 700 may include input 702 for receiving video content.The video content may be received in a raw or uncompressed format, e.g.,8 or 10 bit multi-component pixel values, or may be in a compressed orencoded format. The input 702 may represent a network interface, aperipheral bus interface, or a storage interface. Examples of networkinterface include wired interfaces such as Ethernet, passive opticalnetwork (PON), etc. and wireless interfaces such as Wi-Fi or cellularinterfaces.

The system 700 may include a coding component 704 that may implement thevarious coding or encoding methods described in the present document.The coding component 704 may reduce the average bitrate of video fromthe input 702 to the output of the coding component 704 to produce acoded representation of the video. The coding techniques are thereforesometimes called video compression or video transcoding techniques. Theoutput of the coding component 704 may be either stored, or transmittedvia a communication connected, as represented by the component 706. Thestored or communicated bitstream (or coded) representation of the videoreceived at the input 702 may be used by the component 708 forgenerating pixel values or displayable video that is sent to a displayinterface 710. The process of generating user-viewable video from thebitstream representation is sometimes called video decompression.Furthermore, while certain video processing operations are referred toas “coding” operations or tools, it will be appreciated that the codingtools or operations are used at an encoder and corresponding decodingtools or operations that reverse the results of the coding will beperformed by a decoder.

Examples of a peripheral bus interface or a display interface mayinclude universal serial bus (USB) or high definition multimediainterface (HDMI) or Displayport, and so on. Examples of storageinterfaces include serial advanced technology attachment (SATA),peripheral component interconnect (PCI), integrated drive electronics(IDE) interface, and the like. The techniques described in the presentdocument may be embodied in various electronic devices such as mobilephones, laptops, smartphones or other devices that are capable ofperforming digital data processing and/or video display.

FIG. 8 is a block diagram of a video processing apparatus 800. Theapparatus 800 may be used to implement one or more of the methodsdescribed herein. The apparatus 800 may be embodied in a smartphone,tablet, computer, Internet of Things (IoT) receiver, and so on. Theapparatus 800 may include one or more processors 802, one or morememories 804 and video processing hardware/circuitry 806. Theprocessor(s) 802 may be configured to implement one or more methodsdescribed in the present document (e.g., in FIGS. 5A and 5B). The memory(memories) 804 may be used for storing data and code used forimplementing the methods and techniques described herein. The videoprocessing hardware 806 may be used to implement, in hardware circuitry,some techniques described in the present document. In some embodiments,the hardware 806 may be partly or entirely in the processors 802, e.g.,a graphics processor.

FIG. 9 is a block diagram that illustrates an example video codingsystem 100 that may utilize the techniques of this disclosure. As shownin FIG. 9 , video coding system 100 may include a source device 110 anda destination device 120. Source device 110 generates encoded video datawhich may be referred to as a video encoding device. Destination device120 may decode the encoded video data generated by source device 110which may be referred to as a video decoding device. Source device 110may include a video source 112, a video encoder 114, and an input/output(I/O) interface 116.

Video source 112 may include a source such as a video capture device, aninterface to receive video data from a video content provider, and/or acomputer graphics system for generating video data, or a combination ofsuch sources. The video data may comprise one or more pictures. Videoencoder 114 encodes the video data from video source 112 to generate abitstream. The bitstream may include a sequence of bits that form acoded representation of the video data. The bitstream may include codedpictures and associated data. The coded picture is a codedrepresentation of a picture. The associated data may include sequenceparameter sets, picture parameter sets, and other syntax structures. I/Ointerface 116 may include a modulator/demodulator (modem) and/or atransmitter. The encoded video data may be transmitted directly todestination device 120 via I/O interface 116 through network 130 a. Theencoded video data may also be stored onto a storage medium/server 130 bfor access by destination device 120.

Destination device 120 may include an I/O interface 126, a video decoder124, and a display device 122.

I/O interface 126 may include a receiver and/or a modem. I/O interface126 may acquire encoded video data from the source device 110 or thestorage medium/server 130 b. Video decoder 124 may decode the encodedvideo data. Display device 122 may display the decoded video data to auser. Display device 122 may be integrated with the destination device120, or may be external to destination device 120 which be configured tointerface with an external display device.

Video encoder 114 and video decoder 124 may operate according to a videocompression standard, such as the High Efficiency Video Coding (HEVC)standard, Versatile Video Coding (VVM) standard and other current and/orfurther standards.

FIG. 10 is a block diagram illustrating an example of video encoder 200,which may be video encoder 114 in the system 100 illustrated in FIG. 9 .

Video encoder 200 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 10 , video encoder200 includes a plurality of functional components. The techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 200. In some examples, a processor may be configured toperform any or all of the techniques described in this disclosure.

The functional components of video encoder 200 may include a partitionunit 201, a predication unit 202 which may include a mode select unit203, a motion estimation unit 204, a motion compensation unit 205, anintra prediction unit 206, a residual generation unit 207, a transformunit 208, a quantization unit 209, an inverse quantization unit 210, aninverse transform unit 211, a reconstruction unit 212, a buffer 213, andan entropy encoding unit 214.

In other examples, video encoder 200 may include more, fewer, ordifferent functional components. In an example, predication unit 202 mayinclude an intra block copy (IBC) unit. The IBC unit may performpredication in an IBC mode in which at least one reference picture is apicture where the current video block is located.

Furthermore, some components, such as motion estimation unit 204 andmotion compensation unit 205 may be highly integrated, but arerepresented in the example of FIG. 10 separately for purposes ofexplanation.

Partition unit 201 may partition a picture into one or more videoblocks. Video encoder 200 and video decoder 300 may support variousvideo block sizes.

Mode select unit 203 may select one of the coding modes, intra or inter,e.g., based on error results, and provide the resulting intra- orinter-coded block to a residual generation unit 207 to generate residualblock data and to a reconstruction unit 212 to reconstruct the encodedblock for use as a reference picture. In some example, Mode select unit203 may select a combination of intra and inter predication (CIIP) modein which the predication is based on an inter predication signal and anintra predication signal. Mode select unit 203 may also select aresolution for a motion vector (e.g., a sub-pixel or integer pixelprecision) for the block in the case of inter-predication.

To perform inter prediction on a current video block, motion estimationunit 204 may generate motion information for the current video block bycomparing one or more reference frames from buffer 213 to the currentvideo block. Motion compensation unit 205 may determine a predictedvideo block for the current video block based on the motion informationand decoded samples of pictures from buffer 213 other than the pictureassociated with the current video block.

Motion estimation unit 204 and motion compensation unit 205 may performdifferent operations for a current video block, for example, dependingon whether the current video block is in an I slice, a P slice, or a Bslice.

In some examples, motion estimation unit 204 may perform uni-directionalprediction for the current video block, and motion estimation unit 204may search reference pictures of list 0 or list 1 for a reference videoblock for the current video block. Motion estimation unit 204 may thengenerate a reference index that indicates the reference picture in list0 or list 1 that contains the reference video block and a motion vectorthat indicates a spatial displacement between the current video blockand the reference video block. Motion estimation unit 204 may output thereference index, a prediction direction indicator, and the motion vectoras the motion information of the current video block. Motioncompensation unit 205 may generate the predicted video block of thecurrent block based on the reference video block indicated by the motioninformation of the current video block.

In other examples, motion estimation unit 204 may perform bi-directionalprediction for the current video block, motion estimation unit 204 maysearch the reference pictures in list 0 for a reference video block forthe current video block and may also search the reference pictures inlist 1 for another reference video block for the current video block.Motion estimation unit 204 may then generate reference indexes thatindicate the reference pictures in list 0 and list 1 containing thereference video blocks and motion vectors that indicate spatialdisplacements between the reference video blocks and the current videoblock. Motion estimation unit 204 may output the reference indexes andthe motion vectors of the current video block as the motion informationof the current video block. Motion compensation unit 205 may generatethe predicted video block of the current video block based on thereference video blocks indicated by the motion information of thecurrent video block.

In some examples, motion estimation unit 204 may output a full set ofmotion information for decoding processing of a decoder.

In some examples, motion estimation unit 204 may not output a full setof motion information for the current video. Rather, motion estimationunit 204 may signal the motion information of the current video blockwith reference to the motion information of another video block. Forexample, motion estimation unit 204 may determine that the motioninformation of the current video block is sufficiently similar to themotion information of a neighboring video block.

In one example, motion estimation unit 204 may indicate, in a syntaxstructure associated with the current video block, a value thatindicates to the video decoder 300 that the current video block has thesame motion information as the other video block.

In another example, motion estimation unit 204 may identify, in a syntaxstructure associated with the current video block, another video blockand a motion vector difference (MVD). The motion vector differenceindicates a difference between the motion vector of the current videoblock and the motion vector of the indicated video block. The videodecoder 300 may use the motion vector of the indicated video block andthe motion vector difference to determine the motion vector of thecurrent video block.

As discussed above, video encoder 200 may predictively signal the motionvector. Two examples of predictive signaling techniques that may beimplemented by video encoder 200 include advanced motion vectorpredication (AMVP) and merge mode signaling.

Intra prediction unit 206 may perform intra prediction on the currentvideo block. When intra prediction unit 206 performs intra prediction onthe current video block, intra prediction unit 206 may generateprediction data for the current video block based on decoded samples ofother video blocks in the same picture. The prediction data for thecurrent video block may include a predicted video block and varioussyntax elements.

Residual generation unit 207 may generate residual data for the currentvideo block by subtracting (e.g., indicated by the minus sign) thepredicted video block(s) of the current video block from the currentvideo block. The residual data of the current video block may includeresidual video blocks that correspond to different sample components ofthe samples in the current video block.

In other examples, there may be no residual data for the current videoblock for the current video block, for example in a skip mode, andresidual generation unit 207 may not perform the subtracting operation.

Transform processing unit 208 may generate one or more transformcoefficient video blocks for the current video block by applying one ormore transforms to a residual video block associated with the currentvideo block.

After transform processing unit 208 generates a transform coefficientvideo block associated with the current video block, quantization unit209 may quantize the transform coefficient video block associated withthe current video block based on one or more quantization parameter (QP)values associated with the current video block.

Inverse quantization unit 210 and inverse transform unit 211 may applyinverse quantization and inverse transforms to the transform coefficientvideo block, respectively, to reconstruct a residual video block fromthe transform coefficient video block. Reconstruction unit 212 may addthe reconstructed residual video block to corresponding samples from oneor more predicted video blocks generated by the predication unit 202 toproduce a reconstructed video block associated with the current blockfor storage in the buffer 213.

After reconstruction unit 212 reconstructs the video block, loopfiltering operation may be performed to reduce video blocking artifactsin the video block.

Entropy encoding unit 214 may receive data from other functionalcomponents of the video encoder 200. When entropy encoding unit 214receives the data, entropy encoding unit 214 may perform one or moreentropy encoding operations to generate entropy encoded data and outputa bitstream that includes the entropy encoded data.

FIG. 11 is a block diagram illustrating an example of video decoder 300which may be video decoder 114 in the system 100 illustrated in FIG. 9 .

The video decoder 300 may be configured to perform any or all of thetechniques of this disclosure. In the example of FIG. 11 , the videodecoder 300 includes a plurality of functional components. Thetechniques described in this disclosure may be shared among the variouscomponents of the video decoder 300. In some examples, a processor maybe configured to perform any or all of the techniques described in thisdisclosure.

In the example of FIG. 11 , video decoder 300 includes an entropydecoding unit 301, a motion compensation unit 302, an intra predictionunit 303, an inverse quantization unit 304, an inverse transformationunit 305, and a reconstruction unit 306 and a buffer 307. Video decoder300 may, in some examples, perform a decoding pass generally reciprocalto the encoding pass described with respect to video encoder 200 (FIG.10 ).

Entropy decoding unit 301 may retrieve an encoded bitstream. The encodedbitstream may include entropy coded video data (e.g., encoded blocks ofvideo data). Entropy decoding unit 301 may decode the entropy codedvideo data, and from the entropy decoded video data, motion compensationunit 302 may determine motion information including motion vectors,motion vector precision, reference picture list indexes, and othermotion information. Motion compensation unit 302 may, for example,determine such information by performing the AMVP and merge mode.

Motion compensation unit 302 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used with sub-pixelprecision may be included in the syntax elements.

Motion compensation unit 302 may use interpolation filters as used byvideo encoder 200 during encoding of the video block to calculateinterpolated values for sub-integer pixels of a reference block. Motioncompensation unit 302 may determine the interpolation filters used byvideo encoder 200 according to received syntax information and use theinterpolation filters to produce predictive blocks.

Motion compensation unit 302 may use some of the syntax information todetermine sizes of blocks used to encode frame(s) and/or slice(s) of theencoded video sequence, partition information that describes how eachmacroblock of a picture of the encoded video sequence is partitioned,modes indicating how each partition is encoded, one or more referenceframes (and reference frame lists) for each inter-encoded block, andother information to decode the encoded video sequence.

Intra prediction unit 303 may use intra prediction modes for examplereceived in the bitstream to form a prediction block from spatiallyadjacent blocks. Inverse quantization unit 304 inverse quantizes, i.e.,de-quantizes, the quantized video block coefficients provided in thebitstream and decoded by entropy decoding unit 301. Inverse transformunit 305 applies an inverse transform.

Reconstruction unit 306 may sum the residual blocks with thecorresponding prediction blocks generated by motion compensation unit302 or intra-prediction unit 303 to form decoded blocks. If desired, adeblocking filter may also be applied to filter the decoded blocks inorder to remove blockiness artifacts. The decoded video blocks are thenstored in buffer 307, which provides reference blocks for subsequentmotion compensation/intra predication and also produces decoded videofor presentation on a display device.

FIGS. 12-16 show example methods that can implement the technicalsolutions described above in, for example, the embodiments shown inFIGS. 7-11 .

FIG. 12 shows a flowchart for an example method 1200 of video processingincludes, at operation 1210, determining, for a current video block of avideo coded using an adaptive color transform (ACT) mode, whether ajoint coding of chroma residuals (JCCR) coding tool is enabled for thecurrent video block.

The method 1200 includes, at operation 1220, performing, based on thedetermining, a conversion between the video and a bitstream of thevideo, the bitstream conforming to a rule that specifies that one ormore quantization parameter (QP) offsets used for coding the currentvideo block are signaled when the JCCR coding tool is enabled.

FIG. 13 shows a flowchart for an example method 1300 of video processingincludes, at operation 1310, performing a conversion between a currentvideo block of a video and a bitstream of the video, the bitstreamconforming to a format rule that specifies that a manner by which adelta quantization parameter (QP) is derived or signaled based on acoding information of the current video block.

FIG. 14 shows a flowchart for an example method 1400 of video processingincludes, at operation 1410, performing a conversion between a currentvideo block of a video and a bitstream of the video, the bitstreamconforms to a format rule that specifies that that one or morequantization parameter (QP) offsets used for coding the current videoblock are signaled in a picture parameter set (PPS) associated with thecurrent video block independently of information signaled in a sequenceparameter set (SPS) associated with the current video block.

FIG. 15 shows a flowchart for an example method 1500 of video processingincludes, at operation 1510, performing a conversion between a currentvideo block of a video and a bitstream of the video, the bitstreamconforming to a format rule that specifies a video level at which tosignal one or more quantization parameter (QP) offsets used for codingthe current video block, and the video level being a first level or asecond level that is lower than the first level.

FIG. 16 shows a flowchart for an example method 1600 of video processingincludes, at operation 1610, performing a conversion between a currentvideo block of a video and a bitstream of the video, the bitstreamconforming to a format rule that specifies whether or how an overwritingmechanism is used for signaling a quantization parameter (QP) offsetused for coding the current video block.

A listing of solutions preferred by some embodiments is provided next.

A1. A method of video processing, comprising determining, for a currentvideo block of a video coded using an adaptive color transform (ACT)mode, whether a joint coding of chroma residuals (JCCR) coding tool isenabled for the current video block; and performing, based on thedetermining, a conversion between the video and a bitstream of thevideo, wherein the bitstream conforms to a rule, and wherein the rulespecifies that one or more quantization parameter (QP) offsets used forcoding the current video block are signaled when the JCCR coding tool isenabled.

A2. The method of solution A1, wherein the one or more QP offsets aresignaled in a slice header (SH) when the JCCR coding tool is enabled.

A3. The method of solution A1, wherein the rule further specifieswhether to signal a syntax element indicating whether the one or more QPoffsets are present is based on the JCCR coding tool being enabled.

A4. The method of solution A3, wherein the syntax element is in apicture parameter set (PPS) or a slice header (SH).

A5. The method of solution A3 or A4, wherein the syntax element ispps_joint_cbcr_qp_offset_present_flag orslice_joint_cbcr_qp_offset_present_flag.

A6. A method of video processing, comprising performing a conversionbetween a current video block of a video and a bitstream of the video,wherein the bitstream conforms to a format rule, and wherein the formatrule specifies that a manner by which a delta quantization parameter(QP) is derived or signaled based on a coding information of the currentvideo block.

A7. The method of solution A6, wherein the coding information comprisesa coding mode of the current video block or a previously codedneighboring block of the current video block.

A8. The method of solution A7, wherein the coding mode comprises anadaptive color transform (ACT) mode.

A9. The method of solution A6, wherein deriving and/or signaling thedelta QP is further based on whether the current video block and apreviously coded neighboring block of the current video block used toderive a QP predictor share the same coding information.

A10. The method of solution A6, wherein the coding information comprisesa coding tool applied to the current video block, and wherein aderivation of a QP predictor is based on one or more video blocks towhich the coding tool has been applied.

A11. A method of video processing, comprising performing a conversionbetween a current video block of a video and a bitstream of the video,wherein the bitstream conforms to a format rule, and wherein the formatrule specifies that that one or more quantization parameter (QP) offsetsused for coding the current video block are signaled in a pictureparameter set (PPS) associated with the current video blockindependently of information signaled in a sequence parameter set (SPS)associated with the current video block.

A12. The method of solution A11, wherein a first indication of a colorformat of the video and/or a second indication of enabling a coding modefor the current video block are signaled in the PPS.

A13. A method of video processing, comprising performing a conversionbetween a current video block of a video and a bitstream of the video,wherein the bitstream conforms to a format rule, and wherein the formatrule specifies a video level at which to signal one or more quantizationparameter (QP) offsets used for coding the current video block, whereinthe video level is a first level or a second level that is lower thanthe first level.

A14. The method of solution A13, wherein the first level is a picturelevel and a second level is a slice level.

A15. The method of solution A14, wherein the one or more QP offsets issignaled in the first level.

A16. The method of solution A14, wherein the one or more QP offsets areexcluded from the first level due to the one or more QP offsets beingsignaled in the second level.

A17. The method any of solutions A11 to 16, wherein the one or more QPoffsets are signaled in a picture header (PH) or a slice header (SH).

A18. The method of any of solutions A1 to A17, wherein the conversioncomprises decoding the video from the bitstream.

A19. The method of any of solutions A1 to A17, wherein the conversioncomprises encoding the video into the bitstream.

A20. The method of any of solutions A1 to A17, wherein the conversioncomprises generating the bitstream from the current video block, andwherein the method further comprises storing the bitstream in anon-transitory computer-readable recording medium.

A21. A method of storing a bitstream representing a video to acomputer-readable recording medium, comprising generating a bitstreamfrom a video according to a method described in any one or more ofsolutions A1 to A17; and writing the bitstream to the computer-readablerecording medium.

A22. A video processing apparatus comprising a processor configured toimplement a method recited in any one or more of solutions A1 to A17.

A23. A computer readable medium that stores the bitstream generatedaccording to a method recited in any one or more of solutions A1 to A17.

A24. A computer-readable medium having instructions stored thereon, theinstructions, when executed, causing a processor to implement a methodrecited in one or more of solutions A1 to A23.

A25. A video processing apparatus for storing a bitstream, wherein thevideo processing apparatus is configured to implement a method recitedin any one or more of solutions A1 to A23.

Another listing of solutions preferred by some embodiments is providednext.

B1. A method of video processing, comprising performing a conversionbetween a current video block of a video and a bitstream of the video,wherein the bitstream conforms to a format rule, and wherein the formatrule specifies whether or how an overwriting mechanism is used forsignaling a quantization parameter (QP) offset used for coding thecurrent video block.

B2. The method of solution B1, wherein a first value of the QP offset issignaled in a first level, and wherein the first value is overwritten bya second value of the QP offset signaled in a second level.

B3. The method of solution B2, wherein the first level is higher thanthe second level.

B4. The method of solution B2 or B3, wherein a difference between thefirst set of values and the second set of values is signaled in thesecond level.

B5. The method of solution B2 or B3, wherein a first syntax elementindicating whether the QP offset is allowed to be overwritten issignaled in the first level or the second level.

B6. The method of solution B5, wherein the first syntax element beingequal to one indicates that a QP delta information is signaled in apicture header (PH) and excluded from a slice header (SH) that refers tothe first level.

B7. The method of solution B6, wherein a second syntax element indicatesthat the QP delta information in the PH is used to determine an initialvalue of a QP, and wherein the initial value of the QP is used forcoding the current video block.

B8. The method of solution B5, wherein the first syntax element beingequal to zero indicates that a QP delta information is excluded from apicture header (PH) and signaled in a slice header (SH) that refers tothe first level.

B9. The method of solution B8, wherein a second syntax element indicatesthat the QP delta information in the SH is used to determine an initialvalue of a QP, and wherein the initial value of the QP is used forcoding the current video block.

B10. The method of any of solutions B5 to B9, wherein the first syntaxelement is pps_qp_delta_info_in_ph_flag.

B11. The method of any of solutions B2 to B10, wherein the first levelcomprises a picture parameter set (PPS).

B12. The method of any of solutions B2 to B10, wherein the second levelcomprises a picture header (PH) or a slice header (SH).

B13. The method of solution B1, wherein a first value of the QP offsetis excluded from a first level due to a second value of the QP offset,which is configured to overwrite the first value, is signaled in asecond level.

B14. The method of any of solutions B1 to B13, wherein the conversioncomprises decoding the video from the bitstream.

B15. The method of any of solutions B1 to B13, wherein the conversioncomprises encoding the video into the bitstream.

B16. The method of any of solutions B1 to B13, wherein the conversioncomprises generating the bitstream from the current video block, andwherein the method further comprises storing the bitstream in anon-transitory computer-readable recording medium.

B17. A method of storing a bitstream representing a video to acomputer-readable recording medium, comprising generating a bitstreamfrom a video according to a method described in any one or more ofsolutions B1 to B13; and writing the bitstream to the computer-readablerecording medium.

B18. A video processing apparatus comprising a processor configured toimplement a method recited in any one or more of solutions B1 to B13.

B19. A computer readable medium that stores the bitstream generatedaccording to any one or more of solutions B1 to B13.

B20. A computer-readable medium having instructions stored thereon, theinstructions, when executed, causing a processor to implement a methodrecited in one or more of solutions B1 to B19.

B21. A video processing apparatus for storing a bitstream, wherein thevideo processing apparatus is configured to implement a method recitedin any of solutions B1 to B19.

Yet another listing of solutions preferred by some embodiments isprovided next.

P1. A method of video processing, comprising performing a determinationwhether to enable a chroma block-based delta pulse code modulation(BDPCM) mode for a video block of a video based on whether a usage of anadaptive color transform (ACT) mode and/or a luma BDPCM mode for thevideo block is enabled; and performing a conversion between the videoblock and a bitstream representation of the video according to thedeterminization.

P2. The method of solution P1, wherein a signaling for a first value fora first flag associated with enabling the chroma BDPCM mode isdetermined based on a signaling of the ACT mode being enabled for thevideo block and a signaling of a second value for a second flagassociated with the usage of the luma BDPCM mode.

P3. The method of solution P2, wherein the first value for the firstflag has a false value in response to the ACT mode being enabled and thesecond value for the second flag having a false value.

P4. The method of solution P2, wherein the first value for the firstflag has a true value in response to the second value for the secondflag having a true value.

P5. The method of solution P1, wherein a signaling of the ACT mode forthe video block is conditionally based on a same BDPCM predictiondirection being used for luma samples and chroma samples of the videoblock.

P6. The method of solution P5, wherein the signaling of the ACT mode isindicated after a signaling of the chroma BDPCM mode and the luma BDPCMmode.

P7. The method of solution P1, wherein in response to the usage of theACT mode being enabled, a first value indicative of a first predictiondirection of the chroma BDPCM mode is derived from a second valueindicative of a second prediction direction of the luma BDPCM mode.

P8. The method of solution P7, wherein the first value indicative of thefirst prediction direction of the chroma BDPCM mode is same as thesecond value indicative of the second prediction direction of the lumaBDPCM mode.

P9. The method of solution P8, wherein the first prediction direction ofthe chroma BDPCM mode and the second prediction direction of the lumaBDPCM mode are in a horizontal direction.

P10. The method of solution P8, wherein the first prediction directionof the chroma BDPCM mode and the second prediction direction of the lumaBDPCM mode are in a vertical direction.

P11. The method of solution P1, wherein in response to the usage of theACT mode being disabled, a first value indicative of a first predictiondirection of the chroma BDPCM mode is zero.

P12. A method of video processing, comprising performing a determinationwhether to enable a block-based delta pulse code modulation (BDPCM) modefor a video block of a video based on whether a usage of an adaptivecolor transform (ACT) mode for the video block is enabled; andperforming a conversion between the video block and a bitstreamrepresentation of the video according to the determinization.

P13. The method of solution P12, wherein the BDPCM mode is disabled forthe video block in response to the ACT mode being enabled for the videoblock.

P14. The method of solution P13, wherein a first flag indicative of theBDPCM mode is signaled after a second flag indicative of the ACT mode.

P15. The method of solution P13, wherein a flag indicative of the BDPCMmode is not signaled, wherein the flag is determined to be a false valueor zero.

P16. The method of solution P12, wherein the ACT mode is disabled forthe video block in response to the BDPCM mode being enabled for thevideo block.

P17. The method of solution P16, wherein a first flag indicative of theBDPCM mode is signaled before a second flag indicative of the ACT mode.

P18. The method of solution P16, wherein a flag indicative of the ACTmode is not signaled, wherein the flag is determined to be a false valueor zero.

P19. The method of any of solutions P12 to P18, wherein the BDPCM modeincludes a luma BDPCM mode and/or a chroma BDPCM mode.

P20. The method of solution P1, wherein the ACT mode is applied when thechroma BDPCM mode and the luma BDPCM mode are associated with differentprediction modes.

P21. The method of solution P20, wherein a forward ACT mode is appliedafter the chroma BDPCM mode or the luma BDPCM mode.

P22. The method of any of solution P1 to P21, wherein a quantizationparameter (QP) for the video block is clipped in response to the ACTmode being enabled.

P23. The method of solution P22, wherein a clipping function forclipping the QP is defined as (l, h, x), where l is a lowest possiblevalue of an input x and h is a highest possible value of an input x.

P24. The method of solution P23, wherein l is equal to zero.

P25. The method of solution P23, wherein h is equal to 63.

P26. The method of solution P22, wherein the QP for the video block isclipped after the QP is adjusted for the ACT mode.

P27. The method of solution P23, wherein in response to a transform skipbeing applied to the video block, l is equal to a minimal allowed QP fora transform skip mode.

P28. The method of any of solution P23 to P26, wherein l, h, m, n and/ork are integer numbers that depend on (i) a message signaled in theDPS/SPS/VPS/PPS/APS/picture header/slice header/tile groupheader/Largest coding unit (LCU)/Coding unit (CU)/LCU row/group ofLCUs/TU/PU block/Video coding unit, (ii) a position ofCU/PU/TU/block/Video coding unit, (iii) coded modes of blocks containingthe samples along the edges, (iv) transform matrices applied to theblocks containing the samples along the edges, (v) block dimension/Blockshape of current block and/or its neighboring blocks, (vi) indication ofthe colour format (such as 4:2:0, 4:4:4, RGB or YUV), (vii) a codingtree structure (such as dual tree or single tree), (viii) a slice/tilegroup type and/or picture type, (ix) a colour component (e.g. may beonly applied on Cb or Cr), (x) a temporal layer ID, or (xi)profiles/Levels/Tiers of a standard.

P29. The method of any of solution P23 to P26, wherein l, h, m, n and/ork are signaled to a decoder.

P30. The method of any of solution P30, wherein a color format is 4:2:0or 4:2:2.

P31. The method of any of solutions P1 to P30, wherein an indication forthe ACT mode or the BDPCM mode or the chroma BDPCM mode or the lumaBDPCM mode is signaled in a sequence, a picture, a slice, a tile, abrick, or a video region-level.

P32. A method of video processing, comprising determining that a jointcoding of chroma residuals (JCCR) tool is used on a video block of avideo for which an adaptive color transform (ACT) mode is enabled; andperforming, based on the determining, a conversion between the videoblock and a bitstream representation of the video, wherein aquantization parameter (QP) of the ACT mode is based on a mode of theJCCR tool.

P33. The method of solution P32, wherein the QP is −5 or −6 upon adetermination that the mode of the JCCR tool is 1.

P34. The method of solution P32, wherein the QP is −4 or −5 upon adetermination that the mode of the JCCR tool is 3.

P35. The method of any of solutions P1 to P34, wherein the conversioncomprises parsing and decoding the coded representation to generatevideo pixels.

P36. The method of any of solutions P1 to P34, wherein the conversioncomprises generating the coded representation by encoding the video.

P37. A video decoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions P1 to P36.

P38. A video encoding apparatus comprising a processor configured toimplement a method recited in one or more of solutions P1 to P36.

P39. A computer program product having computer code stored thereon, thecode, when executed by a processor, causes the processor to implement amethod recited in any of solutions P1 to P36.

In the present document, the term “video processing” may refer to videoencoding, video decoding, video compression or video decompression. Forexample, video compression algorithms may be applied during conversionfrom pixel representation of a video to a corresponding bitstreamrepresentation or vice versa. The bitstream representation of a currentvideo block may, for example, correspond to bits that are eitherco-located or spread in different places within the bitstream, as isdefined by the syntax. For example, a macroblock may be encoded in termsof transformed and coded error residual values and also using bits inheaders and other fields in the bitstream.

The disclosed and other solutions, examples, embodiments, modules andthe functional operations described in this document can be implementedin digital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this document and theirstructural equivalents, or in combinations of one or more of them. Thedisclosed and other embodiments can be implemented as one or morecomputer program products, i.e., one or more modules of computer programinstructions encoded on a computer readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium can be a machine-readable storage device, amachine-readable storage substrate, a memory device, a composition ofmatter effecting a machine-readable propagated signal, or a combinationof one or more them. The term “data processing apparatus” encompassesall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, or acombination of one or more of them. A propagated signal is anartificially generated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, that is generated to encodeinformation for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random-access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., erasable programmable read-onlymemory (EPROM), electrically EPROM (EEPROM), and flash memory devices;magnetic disks, e.g., internal hard disks or removable disks; magnetooptical disks; and compact disc read-only memory (CD ROM) and digitalversatile disc read-only memory (DVD-ROM) disks. The processor and thememory can be supplemented by, or incorporated in, special purpose logiccircuitry.

While this patent document contains many specifics, these should not beconstrued as limitations on the scope of any subject matter or of whatmay be claimed, but rather as descriptions of features that may bespecific to particular embodiments of particular techniques. Certainfeatures that are described in this patent document in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described in this patent document should not be understoodas requiring such separation in all embodiments. Only a fewimplementations and examples are described and other implementations,enhancements and variations can be made based on what is described andillustrated in this patent document.

What is claimed is:
 1. A method of processing video data, comprising:performing a conversion between a first video block of a video and abitstream of the video, wherein the bitstream conforms to a rule, andwherein the rule specifies that one or more quantization parameter (QP)offsets used for coding the first video block are signaled at a firstlevel or a second level that is lower than the first level.
 2. Themethod of claim 1, wherein the first level is a picture level and thesecond level is a slice level.
 3. The method of claim 2, wherein the oneor more QP offsets are signaled in the first level when a first syntaxelement is included in the bitstream with a value indicating that theone or more QP offsets are signaled in the first level.
 4. The method ofclaim 3, wherein the one or more QP offsets are excluded from the firstlevel and signaled in the second level when the value of the firstsyntax element indicates that the one or more QP offsets are signaled inthe second level or when the first syntax element is not present in thebitstream.
 5. The method of claim 4, wherein the first syntax element isincluded in a picture parameter set (PPS) when the first syntax elementis included in the bitstream.
 6. The method of claim 2, wherein the oneor more QP offsets are signaled in a picture header (PH) or a sliceheader (SH).
 7. The method of claim 1, further comprising: determining,for a second video block of the video coded using a color transformmode, whether a joint coding of chroma residuals (JCCR) coding tool isenabled for the second video block; wherein performing the conversion isfurther based on the determining whether the JCCR coding tool is enabledfor the second video block, and wherein the rule further specifies thatone or more quantization parameter (QP) offsets for a joint chromacomponent are signaled when the JCCR coding tool is enabled.
 8. Themethod of claim 7, wherein the one or more QP offsets for the jointchroma component are signaled in a slice header (SH) when the JCCRcoding tool is enabled.
 9. The method of claim 7, wherein the rulefurther specifies a second syntax element indicating whether the one ormore QP offsets for the joint chroma component are present in a pictureparameter set (PPS).
 10. The method of claim 9, wherein the secondsyntax element is pps_joint_cbcr_qp_offset_present_flag.
 11. The methodof claim 1, wherein the conversion comprises decoding the video from thebitstream.
 12. The method of claim 1, wherein the conversion comprisesencoding the video into the bitstream.
 13. An apparatus for processingvideo data comprising a processor and a non-transitory memory withinstructions thereon, wherein the instructions upon execution by theprocessor, cause the processor to: perform a conversion between a firstvideo block of a video and a bitstream of the video, wherein thebitstream conforms to a rule, and wherein the rule specifies that one ormore quantization parameter (QP) offsets used for coding the first videoblock are signaled at a first level or a second level that is lower thanthe first level.
 14. The apparatus of claim 13, wherein the first levelis a picture level and the second level is a slice level, wherein theone or more QP offsets are signaled in the first level when a firstsyntax element is included in the bitstream with a value indicating thatthe one or more QP offsets are signaled in the first level, wherein theone or more QP offsets are excluded from the first level and signaled inthe second level when the value of the first syntax element indicatesthat the one or more QP offsets are signaled in the second level or whenthe first syntax element is not present in the bitstream, wherein thefirst syntax element is included in a picture parameter set (PPS) whenthe first syntax element is included in the bitstream, and wherein theone or more QP offsets are signaled in a picture header (PH) or a sliceheader (SH).
 15. The apparatus of claim 13, wherein the processor isfurther caused to: determine, for a second video block of the videocoded using a color transform mode, whether a joint coding of chromaresiduals (JCCR) coding tool is enabled for the second video block;wherein the conversion is performed further based on the determiningwhether the JCCR coding tool is enabled for the second video block,wherein the rule further specifies that one or more quantizationparameter (QP) offsets for a joint chroma component are signaled whenthe JCCR coding tool is enabled, wherein the one or more QP offsets forthe joint chroma component are signaled in a slice header (SH) when theJCCR coding tool is enabled, wherein the rule further specifies a secondsyntax element indicating whether the one or more QP offsets for thejoint chroma component are present in a picture parameter set (PPS), andwherein the second syntax element ispps_joint_cbcr_qp_offset_present_flag.
 16. A non-transitorycomputer-readable storage medium storing instructions that cause aprocessor to: perform a conversion between a first video block of avideo and a bitstream of the video, wherein the bitstream conforms to arule, and wherein the rule specifies that one or more quantizationparameter (QP) offsets used for coding the first video block aresignaled at a first level or a second level that is lower than the firstlevel.
 17. The non-transitory computer-readable storage medium of claim16, wherein the first level is a picture level and the second level is aslice level, wherein the one or more QP offsets are signaled in thefirst level when a first syntax element is included in the bitstreamwith a value indicating that the one or more QP offsets are signaled inthe first level, wherein the one or more QP offsets are excluded fromthe first level and signaled in the second level when the value of thefirst syntax element indicates that the one or more QP offsets aresignaled in the second level or when the first syntax element is notpresent in the bitstream, wherein the first syntax element is includedin a picture parameter set (PPS) when the first syntax element isincluded in the bitstream, and wherein the one or more QP offsets aresignaled in a picture header (PH) or a slice header (SH).
 18. Thenon-transitory computer-readable storage medium of claim 16, wherein theprocessor is further caused to: determine, for a second video block ofthe video coded using a color transform mode, whether a joint coding ofchroma residuals (JCCR) coding tool is enabled for the second videoblock; wherein the conversion is performed further based on thedetermining whether the JCCR coding tool is enabled for the secondvideo, and wherein the rule further specifies that one or morequantization parameter (QP) offsets for a joint chroma component aresignaled when the JCCR coding tool is enabled, wherein the one or moreQP offsets for the joint chroma component are signaled in a slice header(SH) when the JCCR coding tool is enabled, wherein the rule furtherspecifies a second syntax element indicating whether the one or more QPoffsets for the joint chroma component are present in a pictureparameter set (PPS), and wherein the second syntax element ispps_joint_cbcr_qp_offset_present_flag.
 19. A non-transitorycomputer-readable recording medium storing a bitstream of a video whichis generated by a method performed by a video processing apparatus,wherein the method comprises: generating the bitstream for a first videoblock of the video, wherein the bitstream conforms to a rule, andwherein the rule specifies that one or more quantization parameter (QP)offsets used for coding the first video block are signaled at a firstlevel or a second level that is lower than the first level.
 20. Thenon-transitory computer-readable recording medium of claim 19, whereinthe first level is a picture level and the second level is a slicelevel, wherein the one or more QP offsets are signaled in the firstlevel when a first syntax element is included in the bitstream with avalue indicating that the one or more QP offsets are signaled in thefirst level, wherein the one or more QP offsets are excluded from thefirst level and signaled in the second level when the value of the firstsyntax element indicates that the one or more QP offsets are signaled inthe second level or when the first syntax element is not present in thebitstream, wherein the first syntax element is included in a pictureparameter set (PPS) when the first syntax element is included in thebitstream, and wherein the one or more QP offsets are signaled in apicture header (PH) or a slice header (SH), and wherein the methodfurther comprises: determining, for a second video block of the videocoded using a color transform mode, whether a joint coding of chromaresiduals (JCCR) coding tool is enabled for the second video block;wherein performing the conversion is further based on the determiningwhether the JCCR coding tool is enabled for the second video block, andwherein the rule further specifies that one or more quantizationparameter (QP) offsets for a joint chroma component are signaled whenthe JCCR coding tool is enabled, wherein the one or more QP offsets forthe joint chroma component are signaled in a slice header (SH) when theJCCR coding tool is enabled, wherein the rule further specifies a secondsyntax element indicating whether the one or more QP offsets for thejoint chroma component are present in a picture parameter set (PPS), andwherein the second syntax element ispps_joint_cbcr_qp_offset_present_flag.